Set tempo sections to the exact pulse when snapped to a musical grid.
[ardour.git] / libs / ardour / tempo.cc
index c2572ee077950b71226d649b6be832ebb318e12f..15323751b41f59ac1db61eda324dbb3d6cc6bed4 100644 (file)
@@ -73,17 +73,20 @@ Meter::frames_per_bar (const Tempo& tempo, framecnt_t sr) const
 const string TempoSection::xml_state_node_name = "Tempo";
 
 TempoSection::TempoSection (const XMLNode& node)
-       : MetricSection (0.0)
+       : MetricSection (0.0, 0, MusicTime)
        , Tempo (TempoMap::default_tempo())
        , _c_func (0.0)
        , _active (true)
+       , _locked_to_meter (false)
 {
-       const XMLProperty *prop;
+       XMLProperty const * prop;
        LocaleGuard lg;
        BBT_Time bbt;
        double pulse;
        uint32_t frame;
 
+       _legacy_bbt = BBT_Time (0, 0, 0);
+
        if ((prop = node.property ("start")) != 0) {
                if (sscanf (prop->value().c_str(), "%" PRIu32 "|%" PRIu32 "|%" PRIu32,
                            &bbt.bars,
@@ -92,20 +95,18 @@ TempoSection::TempoSection (const XMLNode& node)
                        /* legacy session - start used to be in bbt*/
                        _legacy_bbt = bbt;
                        pulse = -1.0;
-                       set_pulse (pulse);
+                       info << _("Legacy session detected. TempoSection XML node will be altered.") << endmsg;
                }
-       } else {
-               warning << _("TempoSection XML node has no \"start\" property") << endmsg;
        }
 
-
        if ((prop = node.property ("pulse")) != 0) {
-               if (sscanf (prop->value().c_str(), "%lf", &pulse) != 1 || pulse < 0.0) {
-                       error << _("TempoSection XML node has an illegal \"beat\" value") << endmsg;
-               } else {
-                       set_pulse (pulse);
+               if (sscanf (prop->value().c_str(), "%lf", &pulse) != 1) {
+                       error << _("TempoSection XML node has an illegal \"pulse\" value") << endmsg;
                }
        }
+
+       set_pulse (pulse);
+
        if ((prop = node.property ("frame")) != 0) {
                if (sscanf (prop->value().c_str(), "%" PRIu32, &frame) != 1) {
                        error << _("TempoSection XML node has an illegal \"frame\" value") << endmsg;
@@ -155,10 +156,20 @@ TempoSection::TempoSection (const XMLNode& node)
        }
 
        if ((prop = node.property ("lock-style")) == 0) {
-               set_position_lock_style (MusicTime);
+               if (movable()) {
+                       set_position_lock_style (MusicTime);
+               } else {
+                       set_position_lock_style (AudioTime);
+               }
        } else {
                set_position_lock_style (PositionLockStyle (string_2_enum (prop->value(), position_lock_style())));
        }
+
+       if ((prop = node.property ("locked-to-meter")) == 0) {
+               set_locked_to_meter (false);
+       } else {
+               set_locked_to_meter (string_is_affirmative (prop->value()));
+       }
 }
 
 XMLNode&
@@ -182,6 +193,7 @@ TempoSection::get_state() const
        root->add_property ("active", buf);
        root->add_property ("tempo-type", enum_2_string (_type));
        root->add_property ("lock-style", enum_2_string (position_lock_style()));
+       root->add_property ("locked-to-meter", locked_to_meter()?"yes":"no");
 
        return *root;
 }
@@ -198,7 +210,7 @@ double
 TempoSection::tempo_at_frame (const framepos_t& f, const framecnt_t& frame_rate) const
 {
 
-       if (_type == Constant) {
+       if (_type == Constant || _c_func == 0.0) {
                return pulses_per_minute();
        }
 
@@ -207,14 +219,14 @@ TempoSection::tempo_at_frame (const framepos_t& f, const framecnt_t& frame_rate)
 
 /** returns the zero-based frame (relative to session)
    where the tempo in whole pulses per minute occurs in this section.
-   beat b is only used for constant tempos.
+   pulse p is only used for constant tempos.
    note that the tempo map may have multiple such values.
 */
 framepos_t
-TempoSection::frame_at_tempo (const double& ppm, const double& b, const framecnt_t& frame_rate) const
+TempoSection::frame_at_tempo (const double& ppm, const double& p, const framecnt_t& frame_rate) const
 {
-       if (_type == Constant) {
-               return ((b - pulse())  * frames_per_pulse (frame_rate))  + frame();
+       if (_type == Constant || _c_func == 0.0) {
+               return ((p - pulse()) * frames_per_pulse (frame_rate))  + frame();
        }
 
        return minute_to_frame (time_at_pulse_tempo (ppm), frame_rate) + frame();
@@ -225,7 +237,7 @@ double
 TempoSection::tempo_at_pulse (const double& p) const
 {
 
-       if (_type == Constant) {
+       if (_type == Constant || _c_func == 0.0) {
                return pulses_per_minute();
        }
        double const ppm = pulse_tempo_at_pulse (p - pulse());
@@ -239,11 +251,10 @@ TempoSection::tempo_at_pulse (const double& p) const
 double
 TempoSection::pulse_at_tempo (const double& ppm, const framepos_t& f, const framecnt_t& frame_rate) const
 {
-       if (_type == Constant) {
-               double const beats = ((f - frame()) / frames_per_pulse (frame_rate)) + pulse();
-               return  beats;
+       if (_type == Constant || _c_func == 0.0) {
+               double const pulses = ((f - frame()) / frames_per_pulse (frame_rate)) + pulse();
+               return  pulses;
        }
-
        return pulse_at_pulse_tempo (ppm) + pulse();
 }
 
@@ -254,7 +265,7 @@ TempoSection::pulse_at_tempo (const double& ppm, const framepos_t& f, const fram
 double
 TempoSection::pulse_at_frame (const framepos_t& f, const framecnt_t& frame_rate) const
 {
-       if (_type == Constant) {
+       if (_type == Constant || _c_func == 0.0) {
                return ((f - frame()) / frames_per_pulse (frame_rate)) + pulse();
        }
 
@@ -269,7 +280,7 @@ TempoSection::pulse_at_frame (const framepos_t& f, const framecnt_t& frame_rate)
 framepos_t
 TempoSection::frame_at_pulse (const double& p, const framecnt_t& frame_rate) const
 {
-       if (_type == Constant) {
+       if (_type == Constant || _c_func == 0.0) {
                return (framepos_t) floor ((p - pulse()) * frames_per_pulse (frame_rate)) + frame();
        }
 
@@ -305,7 +316,7 @@ The integral over t of our Tempo function (the beat function, which is the durat
 b(t) = T0(e^(ct) - 1) / c
 
 To find the time t at beat duration b, we use the inverse function of the beat function (the time function) which can be shown to be:
-t(b) = log((cb / T0) + 1) / c
+t(b) = log((c.b / T0) + 1) / c
 
 The time t at which Tempo T occurs is a as above:
 t(T) = log(T / T0) / c
@@ -325,6 +336,13 @@ t = b log (Ta / T0) / (T0 (e^(log (Ta / T0)) - 1))
 By substituting our expanded t as a in the c function above, our problem is reduced to:
 c = T0 (e^(log (Ta / T0)) - 1) / b
 
+Of course the word 'beat' has been left loosely defined above.
+In music, a beat is defined by the musical pulse (which comes from the tempo)
+and the meter in use at a particular time (how many  pulse divisions there are in one bar).
+It would be more accurate to substitute the work 'pulse' for 'beat' above.
+
+Anyway ...
+
 We can now store c for future time calculations.
 If the following tempo section (the one that defines c in conjunction with this one)
 is changed or moved, c is no longer valid.
@@ -362,30 +380,30 @@ TempoSection::compute_c_func_frame (const double& end_bpm, const framepos_t& end
        return c_func (end_bpm, frame_to_minute (end_frame - frame(), frame_rate));
 }
 
-framecnt_t
+framepos_t
 TempoSection::minute_to_frame (const double& time, const framecnt_t& frame_rate) const
 {
-       return (framecnt_t) floor ((time * 60.0 * frame_rate) + 0.5);
+       return (framepos_t) floor ((time * 60.0 * frame_rate) + 0.5);
 }
 
 double
-TempoSection::frame_to_minute (const framecnt_t& frame, const framecnt_t& frame_rate) const
+TempoSection::frame_to_minute (const framepos_t& frame, const framecnt_t& frame_rate) const
 {
        return (frame / (double) frame_rate) / 60.0;
 }
 
 /* position function */
 double
-TempoSection::a_func (double end_bpm, double c_func) const
+TempoSection::a_func (double end_ppm, double c_func) const
 {
-       return log (end_bpm / pulses_per_minute()) /  c_func;
+       return log (end_ppm / pulses_per_minute()) /  c_func;
 }
 
 /*function constant*/
 double
-TempoSection::c_func (double end_bpm, double end_time) const
+TempoSection::c_func (double end_ppm, double end_time) const
 {
-       return log (end_bpm / pulses_per_minute()) /  end_time;
+       return log (end_ppm / pulses_per_minute()) /  end_time;
 }
 
 /* tempo in ppm at time in minutes */
@@ -435,12 +453,10 @@ TempoSection::time_at_pulse (const double& pulse) const
 const string MeterSection::xml_state_node_name = "Meter";
 
 MeterSection::MeterSection (const XMLNode& node)
-       : MetricSection (0.0), Meter (TempoMap::default_meter())
+       : MetricSection (0.0, 0, MusicTime), Meter (TempoMap::default_meter())
 {
        XMLProperty const * prop;
-       BBT_Time start;
        LocaleGuard lg;
-       const XMLProperty *prop;
        BBT_Time bbt;
        double pulse = 0.0;
        double beat = 0.0;
@@ -455,14 +471,13 @@ MeterSection::MeterSection (const XMLNode& node)
                        error << _("MeterSection XML node has an illegal \"start\" value") << endmsg;
                } else {
                        /* legacy session - start used to be in bbt*/
+                       info << _("Legacy session detected - MeterSection XML node will be altered.") << endmsg;
                        pulse = -1.0;
                }
-       } else {
-               error << _("MeterSection XML node has no \"start\" property") << endmsg;
        }
 
        if ((prop = node.property ("pulse")) != 0) {
-               if (sscanf (prop->value().c_str(), "%lf", &pulse) != 1 || pulse < 0.0) {
+               if (sscanf (prop->value().c_str(), "%lf", &pulse) != 1) {
                        error << _("MeterSection XML node has an illegal \"pulse\" value") << endmsg;
                }
        }
@@ -470,20 +485,20 @@ MeterSection::MeterSection (const XMLNode& node)
 
        if ((prop = node.property ("beat")) != 0) {
                if (sscanf (prop->value().c_str(), "%lf", &beat) != 1) {
-                       error << _("MeterSection XML node has an illegal \"beat\" vlue") << endmsg;
+                       error << _("MeterSection XML node has an illegal \"beat\" value") << endmsg;
                }
        }
 
        start.first = beat;
 
        if ((prop = node.property ("bbt")) == 0) {
-               error << _("MeterSection XML node has no \"bbt\" property") << endmsg;
+               warning << _("MeterSection XML node has no \"bbt\" property") << endmsg;
        } else if (sscanf (prop->value().c_str(), "%" PRIu32 "|%" PRIu32 "|%" PRIu32,
                    &bbt.bars,
                    &bbt.beats,
                    &bbt.ticks) < 3) {
                error << _("MeterSection XML node has an illegal \"bbt\" value") << endmsg;
-               //throw failed_constructor();
+               throw failed_constructor();
        }
 
        start.second = bbt;
@@ -519,19 +534,23 @@ MeterSection::MeterSection (const XMLNode& node)
                throw failed_constructor();
        }
 
-       if ((prop = node.property ("lock-style")) == 0) {
-               warning << _("MeterSection XML node has no \"lock-style\" property") << endmsg;
-               set_position_lock_style (MusicTime);
-       } else {
-               set_position_lock_style (PositionLockStyle (string_2_enum (prop->value(), position_lock_style())));
-       }
-
        if ((prop = node.property ("movable")) == 0) {
                error << _("MeterSection XML node has no \"movable\" property") << endmsg;
                throw failed_constructor();
        }
 
        set_movable (string_is_affirmative (prop->value()));
+
+       if ((prop = node.property ("lock-style")) == 0) {
+               warning << _("MeterSection XML node has no \"lock-style\" property") << endmsg;
+               if (movable()) {
+                       set_position_lock_style (MusicTime);
+               } else {
+                       set_position_lock_style (AudioTime);
+               }
+       } else {
+               set_position_lock_style (PositionLockStyle (string_2_enum (prop->value(), position_lock_style())));
+       }
 }
 
 XMLNode&
@@ -567,23 +586,48 @@ MeterSection::get_state() const
 /*
   Tempo Map Overview
 
-  We have tempos, which are nice to think of in whole pulses per minute,
-  and meters which divide tempo pulses into bars (via divisions_per_bar)
-  and beats (via note_divisor).
-  Tempos and meters may be locked to audio or music.
-  Because the notion of a beat cannot be determined without both tempo and meter, the first tempo
-  and first meter are special. they must move together, and must be locked to audio.
+  Tempo is the rate of the musical pulse.
+  Meters divide the pulses into measures and beats.
+
+  TempoSections - provide pulses in the form of beats_per_minute() and note_type() where note_type is the division of a whole pulse,
+  and beats_per_minute is the number of note_types in one minute (unlike what its name suggests).
+  Note that Tempo::beats_per_minute() has nothing to do with musical beats.
+
+  MeterSecions - divide pulses into measures (via divisions_per_bar) and beats (via note_divisor).
+
+  Both tempos and meters have a pulse position and a frame position.
+  Meters also have a beat position, which is always 0.0 for the first meter.
+  TempoSections and MeterSections may be locked to either audio or music (position lock style).
+  The lock style determines the 'true' position of the section wich is used to calculate the other postion parameters of the section.
+
+  The first tempo and first meter are special. they must move together, and must be locked to audio.
   Audio locked tempos which lie before the first meter are made inactive.
   They will be re-activated if the first meter is again placed before them.
 
-  Both tempos and meters have a pulse position and a frame position.
-  Recomputing the tempo map is the process where the 'missing' position
-  (pulse in the case of AudioTime and frame for MusicTime) is calculated
-  based on the lock preference (position_lock_style).
+  With tepo sections potentially being ramped, meters provide a way of mapping beats to whole pulses without
+  referring to the tempo function(s) involved as the distance in whole pulses between a meter and a subsequent beat is
+  sb->beat() - meter->beat() / meter->note_divisor().
+  Because every meter falls on a known pulse, (derived from its bar), the rest is easy as the duration in pulses between
+  two meters is of course
+  (meater_b->bar - meter_a->bar) * meter_a->divisions_per_bar / meter_a->note_divisor.
+
+  Below, beat calculations are based on meter sections and all pulse and tempo calculations are based on tempo sections.
+  Beat to frame conversion of course requires the use of meter and tempo.
+
+  Remembering that ramped tempo sections interact, it is important to avoid referring to any other tempos when moving tempo sections,
+  Here, beats (meters) are used to determine the new pulse (see predict_tempo_position())
+
+  Recomputing the map is the process where the 'missing' position
+  (tempo pulse or meter pulse & beat in the case of AudioTime, frame for MusicTime) is calculated.
+  We construct the tempo map by first using the frame or pulse position (depending on position lock style) of each tempo.
+  We then use this tempo map (really just the tempos) to find the pulse or frame position of each meter (again depending on lock style).
+
+  Having done this, we can now find any musical duration by selecting the tempo and meter covering the position (or tempo) in question
+  and querying its appropriate meter/tempo.
 
   It is important to keep the _metrics in an order that makes sense.
-  Because ramped MusicTime and AudioTime tempos can interact with each other
-  and cause reordering, care must be taken to keep _metrics in a solved state.
+  Because ramped MusicTime and AudioTime tempos can interact with each other,
+  reordering is frequent. Care must be taken to keep _metrics in a solved state.
   Solved means ordered by frame or pulse with frame-accurate precision (see check_solved()).
 */
 struct MetricSectionSorter {
@@ -603,8 +647,8 @@ TempoMap::TempoMap (framecnt_t fr)
        _frame_rate = fr;
        BBT_Time start (1, 1, 0);
 
-       TempoSection *t = new TempoSection (0.0, _default_tempo.beats_per_minute(), _default_tempo.note_type(), TempoSection::Constant);
-       MeterSection *m = new MeterSection (0.0, 0.0, start, _default_meter.divisions_per_bar(), _default_meter.note_divisor());
+       TempoSection *t = new TempoSection (0.0, 0, _default_tempo.beats_per_minute(), _default_tempo.note_type(), TempoSection::Ramp, AudioTime);
+       MeterSection *m = new MeterSection (0.0, 0, 0.0, start, _default_meter.divisions_per_bar(), _default_meter.note_divisor(), AudioTime);
 
        t->set_movable (false);
        m->set_movable (false);
@@ -618,6 +662,12 @@ TempoMap::TempoMap (framecnt_t fr)
 
 TempoMap::~TempoMap ()
 {
+       Metrics::const_iterator d = _metrics.begin();
+       while (d != _metrics.end()) {
+               delete (*d);
+               ++d;
+       }
+       _metrics.clear();
 }
 
 void
@@ -648,6 +698,7 @@ TempoMap::remove_tempo_locked (const TempoSection& tempo)
                if (dynamic_cast<TempoSection*> (*i) != 0) {
                        if (tempo.frame() == (*i)->frame()) {
                                if ((*i)->movable()) {
+                                       delete (*i);
                                        _metrics.erase (i);
                                        return true;
                                }
@@ -678,14 +729,28 @@ TempoMap::remove_meter (const MeterSection& tempo, bool complete_operation)
 }
 
 bool
-TempoMap::remove_meter_locked (const MeterSection& tempo)
+TempoMap::remove_meter_locked (const MeterSection& meter)
 {
        Metrics::iterator i;
 
+       for (i = _metrics.begin(); i != _metrics.end(); ++i) {
+               TempoSection* t = 0;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (meter.frame() == (*i)->frame()) {
+                               if (t->locked_to_meter()) {
+                                       delete (*i);
+                                       _metrics.erase (i);
+                                       break;
+                               }
+                       }
+               }
+       }
+
        for (i = _metrics.begin(); i != _metrics.end(); ++i) {
                if (dynamic_cast<MeterSection*> (*i) != 0) {
-                       if (tempo.frame() == (*i)->frame()) {
+                       if (meter.frame() == (*i)->frame()) {
                                if ((*i)->movable()) {
+                                       delete (*i);
                                        _metrics.erase (i);
                                        return true;
                                }
@@ -705,14 +770,13 @@ TempoMap::do_insert (MetricSection* section)
         */
        MeterSection* m = 0;
        if ((m = dynamic_cast<MeterSection*>(section)) != 0) {
-               //assert (m->bbt().ticks == 0);
 
                if ((m->bbt().beats != 1) || (m->bbt().ticks != 0)) {
 
-                       pair<double, BBT_Time> corrected = make_pair (m->pulse(), m->bbt());
+                       pair<double, BBT_Time> corrected = make_pair (m->beat(), m->bbt());
                        corrected.second.beats = 1;
                        corrected.second.ticks = 0;
-                       corrected.first = bbt_to_beats_locked (_metrics, corrected.second);
+                       corrected.first = beat_at_bbt_locked (_metrics, corrected.second);
                        warning << string_compose (_("Meter changes can only be positioned on the first beat of a bar. Moving from %1 to %2"),
                                                   m->bbt(), corrected.second) << endmsg;
                        //m->set_pulse (corrected);
@@ -748,8 +812,13 @@ TempoMap::do_insert (MetricSection* section)
 
                                        *(dynamic_cast<Tempo*>(*i)) = *(dynamic_cast<Tempo*>(insert_tempo));
                                        (*i)->set_position_lock_style (AudioTime);
+                                       TempoSection* t;
+                                       if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
+                                               t->set_type (insert_tempo->type());
+                                       }
                                        need_add = false;
                                } else {
+                                       delete (*i);
                                        _metrics.erase (i);
                                }
                                break;
@@ -761,7 +830,7 @@ TempoMap::do_insert (MetricSection* section)
 
                        bool const ipm = insert_meter->position_lock_style() == MusicTime;
 
-                       if ((ipm && meter->pulse() == insert_meter->pulse()) || (!ipm && meter->frame() == insert_meter->frame())) {
+                       if ((ipm && meter->beat() == insert_meter->beat()) || (!ipm && meter->frame() == insert_meter->frame())) {
 
                                if (!meter->movable()) {
 
@@ -771,11 +840,11 @@ TempoMap::do_insert (MetricSection* section)
                                         */
 
                                        *(dynamic_cast<Meter*>(*i)) = *(dynamic_cast<Meter*>(insert_meter));
-                                       (*i)->set_position_lock_style (insert_meter->position_lock_style());
+                                       (*i)->set_position_lock_style (AudioTime);
                                        need_add = false;
                                } else {
+                                       delete (*i);
                                        _metrics.erase (i);
-
                                }
 
                                break;
@@ -799,7 +868,7 @@ TempoMap::do_insert (MetricSection* section)
 
                                if (meter) {
                                        bool const ipm = insert_meter->position_lock_style() == MusicTime;
-                                       if ((ipm && meter->pulse() > insert_meter->pulse()) || (!ipm && meter->frame() > insert_meter->frame())) {
+                                       if ((ipm && meter->beat() > insert_meter->beat()) || (!ipm && meter->frame() > insert_meter->frame())) {
                                                break;
                                        }
                                }
@@ -818,44 +887,40 @@ TempoMap::do_insert (MetricSection* section)
                }
 
                _metrics.insert (i, section);
-               //dump (_metrics, std::cerr);
+               //dump (_metrics, std::cout);
        }
 }
 
-void
-TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const double& pulse, TempoSection::Type type)
+TempoSection*
+TempoMap::add_tempo (const Tempo& tempo, const double& pulse, const framepos_t& frame, ARDOUR::TempoSection::Type type, PositionLockStyle pls)
 {
+       TempoSection* ts = 0;
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
-               TempoSection& first (first_tempo());
-               if (ts.pulse() != first.pulse()) {
-                       remove_tempo_locked (ts);
-                       add_tempo_locked (tempo, pulse, true, type);
-               } else {
-                       first.set_type (type);
-                       {
-                               /* cannot move the first tempo section */
-                               *static_cast<Tempo*>(&first) = tempo;
-                               recompute_map (_metrics);
-                       }
-               }
+               ts = add_tempo_locked (tempo, pulse, frame, type, pls, true);
        }
 
+
        PropertyChanged (PropertyChange ());
+
+       return ts;
 }
 
 void
-TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const framepos_t& frame, TempoSection::Type type)
+TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const double& pulse, const framepos_t& frame, TempoSection::Type type, PositionLockStyle pls)
 {
+       const bool locked_to_meter = ts.locked_to_meter();
+
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
                TempoSection& first (first_tempo());
                if (ts.frame() != first.frame()) {
                        remove_tempo_locked (ts);
-                       add_tempo_locked (tempo, frame, true, type);
+                       add_tempo_locked (tempo, pulse, frame, type, pls, true, locked_to_meter);
                } else {
                        first.set_type (type);
                        first.set_pulse (0.0);
+                       first.set_frame (frame);
                        first.set_position_lock_style (AudioTime);
                        {
                                /* cannot move the first tempo section */
@@ -868,87 +933,60 @@ TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const frame
        PropertyChanged (PropertyChange ());
 }
 
-void
-TempoMap::add_tempo (const Tempo& tempo, const double& pulse, ARDOUR::TempoSection::Type type)
-{
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               add_tempo_locked (tempo, pulse, true, type);
-       }
-
-       PropertyChanged (PropertyChange ());
-}
-
-void
-TempoMap::add_tempo (const Tempo& tempo, const framepos_t& frame, ARDOUR::TempoSection::Type type)
-{
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               add_tempo_locked (tempo, frame, true, type);
-       }
-
-
-       PropertyChanged (PropertyChange ());
-}
-
-void
-TempoMap::add_tempo_locked (const Tempo& tempo, double pulse, bool recompute, ARDOUR::TempoSection::Type type)
+TempoSection*
+TempoMap::add_tempo_locked (const Tempo& tempo, double pulse, framepos_t frame
+                           , TempoSection::Type type, PositionLockStyle pls, bool recompute, bool locked_to_meter)
 {
-       TempoSection* ts = new TempoSection (pulse, tempo.beats_per_minute(), tempo.note_type(), type);
+       TempoSection* t = new TempoSection (pulse, frame, tempo.beats_per_minute(), tempo.note_type(), type, pls);
+       t->set_locked_to_meter (locked_to_meter);
 
-       do_insert (ts);
+       do_insert (t);
 
        if (recompute) {
-               solve_map (_metrics, ts, Tempo (ts->beats_per_minute(), ts->note_type()), ts->pulse());
+               if (pls == AudioTime) {
+                       solve_map_frame (_metrics, t, t->frame());
+               } else {
+                       solve_map_pulse (_metrics, t, t->pulse());
+               }
+               recompute_meters (_metrics);
        }
-}
-
-void
-TempoMap::add_tempo_locked (const Tempo& tempo, framepos_t frame, bool recompute, ARDOUR::TempoSection::Type type)
-{
-       TempoSection* ts = new TempoSection (frame, tempo.beats_per_minute(), tempo.note_type(), type);
-
-       do_insert (ts);
 
-       if (recompute) {
-               solve_map (_metrics, ts, Tempo (ts->beats_per_minute(), ts->note_type()), ts->frame());
-       }
+       return t;
 }
 
-void
-TempoMap::replace_meter (const MeterSection& ms, const Meter& meter, const BBT_Time& where)
+MeterSection*
+TempoMap::add_meter (const Meter& meter, const double& beat, const Timecode::BBT_Time& where, const framepos_t& frame, PositionLockStyle pls)
 {
+       MeterSection* m = 0;
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
-               MeterSection& first (first_meter());
+               m = add_meter_locked (meter, beat, where, frame, pls, true);
+       }
 
-               const PositionLockStyle pl = ms.position_lock_style();
-               if (ms.pulse() != first.pulse()) {
-                       remove_meter_locked (ms);
-                       add_meter_locked (meter, bbt_to_beats_locked (_metrics, where), where, true);
-               } else {
-                       /* cannot move the first meter section */
-                       *static_cast<Meter*>(&first) = meter;
-                       first.set_position_lock_style (pl);
-                       recompute_map (_metrics);
-               }
+
+#ifndef NDEBUG
+       if (DEBUG_ENABLED(DEBUG::TempoMap)) {
+               dump (_metrics, std::cerr);
        }
+#endif
 
        PropertyChanged (PropertyChange ());
+       return m;
 }
 
 void
-TempoMap::replace_meter (const MeterSection& ms, const Meter& meter, const framepos_t& frame)
+TempoMap::replace_meter (const MeterSection& ms, const Meter& meter, const BBT_Time& where, const framepos_t& frame, PositionLockStyle pls)
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
-               MeterSection& first (first_meter());
-               TempoSection& first_t (first_tempo());
+               const double beat = beat_at_bbt_locked (_metrics, where);
 
-               if (ms.pulse() != first.pulse()) {
+               if (ms.movable()) {
                        remove_meter_locked (ms);
-                       add_meter_locked (meter, frame, true);
+                       add_meter_locked (meter, beat, where, frame, pls, true);
                } else {
+                       MeterSection& first (first_meter());
+                       TempoSection& first_t (first_tempo());
                        /* cannot move the first meter section */
                        *static_cast<Meter*>(&first) = meter;
                        first.set_position_lock_style (AudioTime);
@@ -956,407 +994,144 @@ TempoMap::replace_meter (const MeterSection& ms, const Meter& meter, const frame
                        first.set_frame (frame);
                        pair<double, BBT_Time> beat = make_pair (0.0, BBT_Time (1, 1, 0));
                        first.set_beat (beat);
-                       recompute_meters (_metrics);
                        first_t.set_frame (first.frame());
                        first_t.set_pulse (0.0);
                        first_t.set_position_lock_style (AudioTime);
-
                        recompute_map (_metrics);
                }
        }
+
        PropertyChanged (PropertyChange ());
 }
 
-
-void
-TempoMap::add_meter (const Meter& meter, const double& beat, const BBT_Time& where)
+MeterSection*
+TempoMap::add_meter_locked (const Meter& meter, double beat, const Timecode::BBT_Time& where, framepos_t frame, PositionLockStyle pls, bool recompute)
 {
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               add_meter_locked (meter, beat, where, true);
+       const MeterSection& prev_m = meter_section_at_frame_locked  (_metrics, frame - 1);
+       const double pulse = ((where.bars - prev_m.bbt().bars) * (prev_m.divisions_per_bar() / prev_m.note_divisor())) + prev_m.pulse();
+
+       if (pls == AudioTime) {
+               /* add meter-locked tempo */
+               add_tempo_locked (tempo_at_frame_locked (_metrics, frame), pulse,  frame, TempoSection::Ramp, AudioTime, true, true);
        }
 
+       MeterSection* new_meter = new MeterSection (pulse, frame, beat, where, meter.divisions_per_bar(), meter.note_divisor(), pls);
 
-#ifndef NDEBUG
-       if (DEBUG_ENABLED(DEBUG::TempoMap)) {
-               dump (_metrics, std::cerr);
+       do_insert (new_meter);
+
+       if (recompute) {
+
+               if (pls == AudioTime) {
+                       solve_map_frame (_metrics, new_meter, frame);
+               } else {
+                       solve_map_bbt (_metrics, new_meter, where);
+               }
        }
-#endif
 
-       PropertyChanged (PropertyChange ());
+       return new_meter;
 }
 
 void
-TempoMap::add_meter (const Meter& meter, const framepos_t& frame)
+TempoMap::change_initial_tempo (double beats_per_minute, double note_type)
 {
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               add_meter_locked (meter, frame, true);
-       }
-
+       Tempo newtempo (beats_per_minute, note_type);
+       TempoSection* t;
 
-#ifndef NDEBUG
-       if (DEBUG_ENABLED(DEBUG::TempoMap)) {
-               dump (_metrics, std::cerr);
+       for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
+                       {
+                               Glib::Threads::RWLock::WriterLock lm (lock);
+                               *((Tempo*) t) = newtempo;
+                               recompute_map (_metrics);
+                       }
+                       PropertyChanged (PropertyChange ());
+                       break;
+               }
        }
-#endif
-
-       PropertyChanged (PropertyChange ());
 }
 
 void
-TempoMap::add_meter_locked (const Meter& meter, double beat, BBT_Time where, bool recompute)
+TempoMap::change_existing_tempo_at (framepos_t where, double beats_per_minute, double note_type)
 {
-       /* a new meter always starts a new bar on the first beat. so
-          round the start time appropriately. remember that
-          `where' is based on the existing tempo map, not
-          the result after we insert the new meter.
+       Tempo newtempo (beats_per_minute, note_type);
 
-       */
+       TempoSection* prev;
+       TempoSection* first;
+       Metrics::iterator i;
 
-       if (where.beats != 1) {
-               where.beats = 1;
-               where.bars++;
-       }
-       /* new meters *always* start on a beat. */
-       where.ticks = 0;
-       double pulse = pulse_at_beat_locked (_metrics, beat);
+       /* find the TempoSection immediately preceding "where"
+        */
 
-       MeterSection* new_meter = new MeterSection (pulse, beat, where, meter.divisions_per_bar(), meter.note_divisor());
-       do_insert (new_meter);
+       for (first = 0, i = _metrics.begin(), prev = 0; i != _metrics.end(); ++i) {
 
-       if (recompute) {
-               solve_map (_metrics, new_meter, Meter (meter.divisions_per_bar(), meter.note_divisor()), pulse);
-       }
+               if ((*i)->frame() > where) {
+                       break;
+               }
 
-}
+               TempoSection* t;
 
-void
-TempoMap::add_meter_locked (const Meter& meter, framepos_t frame, bool recompute)
-{
+               if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
+                       if (!first) {
+                               first = t;
+                       }
+                       prev = t;
+               }
+       }
+
+       if (!prev) {
+               if (!first) {
+                       error << string_compose (_("no tempo sections defined in tempo map - cannot change tempo @ %1"), where) << endmsg;
+                       return;
+               }
 
-       MeterSection* new_meter = new MeterSection (frame, 0.0, meter.divisions_per_bar(), meter.note_divisor());
+               prev = first;
+       }
 
-       do_insert (new_meter);
+       /* reset */
 
-       if (recompute) {
-               solve_map (_metrics, new_meter, Meter (new_meter->divisions_per_bar(), new_meter->note_divisor()), frame);
+       {
+               Glib::Threads::RWLock::WriterLock lm (lock);
+               /* cannot move the first tempo section */
+               *((Tempo*)prev) = newtempo;
+               recompute_map (_metrics);
        }
 
+       PropertyChanged (PropertyChange ());
 }
 
-/**
-* This is for a gui that needs to know the frame of a tempo section if it were to be moved to some bbt time,
-* taking any possible reordering as a consequence of this into account.
-* @param section - the section to be altered
-* @param bpm - the new Tempo
-* @param bbt - the bbt where the altered tempo will fall
-* @return returns - the position in frames where the new tempo section will lie.
-*/
-framepos_t
-TempoMap::predict_tempo_frame (TempoSection* section, const Tempo& bpm, const BBT_Time& bbt)
+const MeterSection&
+TempoMap::first_meter () const
 {
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       Metrics future_map;
-       framepos_t ret = 0;
-       TempoSection* new_section = copy_metrics_and_point (future_map, section);
+       const MeterSection *m = 0;
 
-       double const beat = bbt_to_beats_locked (future_map, bbt);
-       if (solve_map (future_map, new_section, bpm, pulse_at_beat_locked (future_map, beat))) {
-               ret = new_section->frame();
-       } else {
-               ret = frame_at_beat_locked (_metrics, beat);
+       for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+               if ((m = dynamic_cast<const MeterSection *> (*i)) != 0) {
+                       return *m;
+               }
        }
 
-       Metrics::const_iterator d = future_map.begin();
-       while (d != future_map.end()) {
-               delete (*d);
-               ++d;
-       }
-       return ret;
+       fatal << _("programming error: no meter section in tempo map!") << endmsg;
+       abort(); /*NOTREACHED*/
+       return *m;
 }
 
-double
-TempoMap::predict_tempo_pulse (TempoSection* section, const Tempo& bpm, const framepos_t& frame)
+MeterSection&
+TempoMap::first_meter ()
 {
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       Metrics future_map;
-       double ret = 0.0;
-       TempoSection* new_section = copy_metrics_and_point (future_map, section);
+       MeterSection *m = 0;
 
-       if (solve_map (future_map, new_section, bpm, frame)) {
-               ret = new_section->pulse();
-       } else {
-               ret = pulse_at_frame_locked (_metrics, frame);
-       }
+       /* CALLER MUST HOLD LOCK */
 
-       Metrics::const_iterator d = future_map.begin();
-       while (d != future_map.end()) {
-               delete (*d);
-               ++d;
-       }
-       return ret;
-}
-
-void
-TempoMap::gui_move_tempo_frame (TempoSection* ts,  const Tempo& bpm, const framepos_t& frame)
-{
-       Metrics future_map;
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               TempoSection* new_section = copy_metrics_and_point (future_map, ts);
-               if (solve_map (future_map, new_section, bpm, frame)) {
-                       solve_map (_metrics, ts, bpm, frame);
-               }
-       }
-
-       Metrics::const_iterator d = future_map.begin();
-       while (d != future_map.end()) {
-               delete (*d);
-               ++d;
-       }
-
-       MetricPositionChanged (); // Emit Signal
-}
-
-void
-TempoMap::gui_move_tempo_beat (TempoSection* ts,  const Tempo& bpm, const double& beat)
-{
-       Metrics future_map;
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               TempoSection* new_section = copy_metrics_and_point (future_map, ts);
-               if (solve_map (future_map, new_section, bpm, pulse_at_beat_locked (future_map, beat))) {
-                       solve_map (_metrics, ts, bpm,  pulse_at_beat_locked (_metrics, beat));
-               }
-       }
-
-       Metrics::const_iterator d = future_map.begin();
-       while (d != future_map.end()) {
-               delete (*d);
-               ++d;
-       }
-
-       MetricPositionChanged (); // Emit Signal
-}
-
-void
-TempoMap::gui_move_meter (MeterSection* ms, const Meter& mt, const framepos_t&  frame)
-{
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               solve_map (_metrics, ms, mt, frame);
-       }
-
-       MetricPositionChanged (); // Emit Signal
-}
-
-void
-TempoMap::gui_move_meter (MeterSection* ms, const Meter& mt, const double&  beat)
-{
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               solve_map (_metrics, ms, mt, pulse_at_beat_locked (_metrics, beat));
-       }
-
-       MetricPositionChanged (); // Emit Signal
-}
-
-bool
-TempoMap::gui_change_tempo (TempoSection* ts,  const Tempo& bpm)
-{
-       Metrics future_map;
-       bool can_solve = false;
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               TempoSection* new_section = copy_metrics_and_point (future_map, ts);
-               new_section->set_beats_per_minute (bpm.beats_per_minute());
-               recompute_tempos (future_map);
-
-               if (check_solved (future_map, true)) {
-                       ts->set_beats_per_minute (bpm.beats_per_minute());
-                       recompute_map (_metrics);
-                       can_solve = true;
-               }
-       }
-
-       Metrics::const_iterator d = future_map.begin();
-       while (d != future_map.end()) {
-               delete (*d);
-               ++d;
-       }
-       if (can_solve) {
-               MetricPositionChanged (); // Emit Signal
-       }
-       return can_solve;
-}
-
-TempoSection*
-TempoMap::copy_metrics_and_point (Metrics& copy, TempoSection* section)
-{
-       TempoSection* t;
-       TempoSection* ret = 0;
-       MeterSection* m;
-
-       for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
-               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
-                       if (t == section) {
-                               if (t->position_lock_style() == MusicTime) {
-                                       ret = new TempoSection (t->pulse(), t->beats_per_minute(), t->note_type(), t->type());
-                               } else {
-                                       ret = new TempoSection (t->frame(), t->beats_per_minute(), t->note_type(), t->type());
-                               }
-                               ret->set_active (t->active());
-                               ret->set_movable (t->movable());
-                               copy.push_back (ret);
-                               continue;
-                       }
-                       TempoSection* cp = 0;
-                       if (t->position_lock_style() == MusicTime) {
-                               cp = new TempoSection (t->pulse(), t->beats_per_minute(), t->note_type(), t->type());
-                       } else {
-                               cp = new TempoSection (t->frame(), t->beats_per_minute(), t->note_type(), t->type());
-                       }
-                       cp->set_active (t->active());
-                       cp->set_movable (t->movable());
-                       copy.push_back (cp);
-               }
-               if ((m = dynamic_cast<MeterSection *> (*i)) != 0) {
-                       if (m->position_lock_style() == MusicTime) {
-                               copy.push_back (new MeterSection (m->pulse(), m->beat(), m->bbt(), m->divisions_per_bar(), m->note_divisor()));
-                       } else {
-                               copy.push_back (new MeterSection (m->frame(), m->beat(), m->divisions_per_bar(), m->note_divisor()));
-                       }
-               }
-       }
-       recompute_map (copy);
-       return ret;
-}
-
-bool
-TempoMap::can_solve_bbt (TempoSection* ts,  const Tempo& bpm, const BBT_Time& bbt)
-{
-       Metrics copy;
-       TempoSection* new_section = 0;
-
-       {
-               Glib::Threads::RWLock::ReaderLock lm (lock);
-               new_section = copy_metrics_and_point (copy, ts);
-       }
-
-       double const beat = bbt_to_beats_locked (copy, bbt);
-       bool ret = solve_map (copy, new_section, bpm, pulse_at_beat_locked (copy, beat));
-
-       Metrics::const_iterator d = copy.begin();
-       while (d != copy.end()) {
-               delete (*d);
-               ++d;
-       }
-
-       return ret;
-}
-
-void
-TempoMap::change_initial_tempo (double beats_per_minute, double note_type)
-{
-       Tempo newtempo (beats_per_minute, note_type);
-       TempoSection* t;
-
-       for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
-               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
-                       if (!t->active()) {
-                               continue;
-                       }
-                       {
-                               Glib::Threads::RWLock::WriterLock lm (lock);
-                               *((Tempo*) t) = newtempo;
-                               recompute_map (_metrics);
-                       }
-                       PropertyChanged (PropertyChange ());
-                       break;
-               }
-       }
-}
-
-void
-TempoMap::change_existing_tempo_at (framepos_t where, double beats_per_minute, double note_type)
-{
-       Tempo newtempo (beats_per_minute, note_type);
-
-       TempoSection* prev;
-       TempoSection* first;
-       Metrics::iterator i;
-
-       /* find the TempoSection immediately preceding "where"
-        */
-
-       for (first = 0, i = _metrics.begin(), prev = 0; i != _metrics.end(); ++i) {
-
-               if ((*i)->frame() > where) {
-                       break;
-               }
-
-               TempoSection* t;
-
-               if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
-                       if (!t->active()) {
-                               continue;
-                       }
-                       if (!first) {
-                               first = t;
-                       }
-                       prev = t;
-               }
-       }
-
-       if (!prev) {
-               if (!first) {
-                       error << string_compose (_("no tempo sections defined in tempo map - cannot change tempo @ %1"), where) << endmsg;
-                       return;
-               }
-
-               prev = first;
-       }
-
-       /* reset */
-
-       {
-               Glib::Threads::RWLock::WriterLock lm (lock);
-               /* cannot move the first tempo section */
-               *((Tempo*)prev) = newtempo;
-               recompute_map (_metrics);
-       }
-
-       PropertyChanged (PropertyChange ());
-}
-
-const MeterSection&
-TempoMap::first_meter () const
-{
-       const MeterSection *m = 0;
-
-       for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
-               if ((m = dynamic_cast<const MeterSection *> (*i)) != 0) {
-                       return *m;
-               }
-       }
-
-       fatal << _("programming error: no meter section in tempo map!") << endmsg;
-       abort(); /*NOTREACHED*/
-       return *m;
-}
-
-MeterSection&
-TempoMap::first_meter ()
-{
-       MeterSection *m = 0;
-
-       /* CALLER MUST HOLD LOCK */
-
-       for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
-               if ((m = dynamic_cast<MeterSection *> (*i)) != 0) {
-                       return *m;
-               }
+       for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+               if ((m = dynamic_cast<MeterSection *> (*i)) != 0) {
+                       return *m;
+               }
        }
 
        fatal << _("programming error: no tempo section in tempo map!") << endmsg;
@@ -1376,7 +1151,9 @@ TempoMap::first_tempo () const
                        if (!t->active()) {
                                continue;
                        }
-                       return *t;
+                       if (!t->movable()) {
+                               return *t;
+                       }
                }
        }
 
@@ -1395,7 +1172,9 @@ TempoMap::first_tempo ()
                        if (!t->active()) {
                                continue;
                        }
-                       return *t;
+                       if (!t->movable()) {
+                               return *t;
+                       }
                }
        }
 
@@ -1406,7 +1185,7 @@ TempoMap::first_tempo ()
 void
 TempoMap::recompute_tempos (Metrics& metrics)
 {
-       TempoSection* prev_ts = 0;
+       TempoSection* prev_t = 0;
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
@@ -1415,62 +1194,103 @@ TempoMap::recompute_tempos (Metrics& metrics)
                        if (!t->active()) {
                                continue;
                        }
-                       if (prev_ts) {
+                       if (!t->movable()) {
+                               if (!prev_t) {
+                                       t->set_pulse (0.0);
+                                       prev_t = t;
+                                       continue;
+                               }
+                       }
+                       if (prev_t) {
                                if (t->position_lock_style() == AudioTime) {
-                                       prev_ts->set_c_func (prev_ts->compute_c_func_frame (t->pulses_per_minute(), t->frame(), _frame_rate));
-                                       t->set_pulse (prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate));
+                                       prev_t->set_c_func (prev_t->compute_c_func_frame (t->pulses_per_minute(), t->frame(), _frame_rate));
+                                       if (!t->locked_to_meter()) {
+                                               t->set_pulse (prev_t->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate));
+                                       }
 
                                } else {
-                                       prev_ts->set_c_func (prev_ts->compute_c_func_pulse (t->pulses_per_minute(), t->pulse(), _frame_rate));
-                                       t->set_frame (prev_ts->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate));
+                                       prev_t->set_c_func (prev_t->compute_c_func_pulse (t->pulses_per_minute(), t->pulse(), _frame_rate));
+                                       t->set_frame (prev_t->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate));
 
                                }
                        }
-                       prev_ts = t;
+                       prev_t = t;
                }
        }
-       prev_ts->set_c_func (0.0);
+       prev_t->set_c_func (0.0);
 }
 
-/* tempos must be positioned correctly */
+/* tempos must be positioned correctly.
+   the current approach is to use a meter's bbt time as its base position unit.
+   an audio-locked meter requires a recomputation of pulse and beat (but not bbt),
+   while a music-locked meter requires recomputations of frame pulse and beat (but not bbt)
+*/
 void
 TempoMap::recompute_meters (Metrics& metrics)
 {
        MeterSection* meter = 0;
        MeterSection* prev_m = 0;
-       double accumulated_beats = 0.0;
-       uint32_t accumulated_bars = 0;
 
        for (Metrics::const_iterator mi = metrics.begin(); mi != metrics.end(); ++mi) {
                if ((meter = dynamic_cast<MeterSection*> (*mi)) != 0) {
-                       if (prev_m) {
-                               const double beats_in_m = (meter->pulse() - prev_m->pulse()) * prev_m->note_divisor();
-                               accumulated_beats += beats_in_m;
-                               accumulated_bars += (beats_in_m + 1) / prev_m->divisions_per_bar();
-                       }
                        if (meter->position_lock_style() == AudioTime) {
                                double pulse = 0.0;
-                               pair<double, BBT_Time> bt = make_pair (accumulated_beats, BBT_Time (accumulated_bars + 1, 1, 0));
-                               meter->set_beat (bt);
+                               pair<double, BBT_Time> b_bbt;
+                               TempoSection* meter_locked_tempo = 0;
+                               for (Metrics::const_iterator ii = metrics.begin(); ii != metrics.end(); ++ii) {
+                                       TempoSection* t;
+                                       if ((t = dynamic_cast<TempoSection*> (*ii)) != 0) {
+                                               if ((t->locked_to_meter() || !t->movable()) && t->frame() == meter->frame()) {
+                                                       meter_locked_tempo = t;
+                                                       break;
+                                               }
+                                       }
+                               }
+
                                if (prev_m) {
-                                       pulse = prev_m->pulse() + (meter->beat() - prev_m->beat()) / prev_m->note_divisor();
-                               } else {
-                                       if (meter->movable()) {
-                                               pulse = pulse_at_frame_locked (metrics, meter->frame());
-                                       } else {
-                                               pulse = 0.0;
+                                       const double beats = (meter->bbt().bars - prev_m->bbt().bars) * prev_m->divisions_per_bar();
+                                       if (beats + prev_m->beat() != meter->beat()) {
+                                               /* reordering caused a bbt change */
+                                               b_bbt = make_pair (beats + prev_m->beat()
+                                                                  , BBT_Time ((beats / prev_m->divisions_per_bar()) + prev_m->bbt().bars, 1, 0));
+                                               pulse = prev_m->pulse() + (beats / prev_m->note_divisor());
+
+                                       } else if (meter->movable()) {
+                                               b_bbt = make_pair (meter->beat(), meter->bbt());
+                                               pulse = prev_m->pulse() + (beats / prev_m->note_divisor());
                                        }
+                               } else {
+                                       b_bbt = make_pair (0.0, BBT_Time (1, 1, 0));
                                }
+                               if (meter_locked_tempo) {
+                                       meter_locked_tempo->set_pulse (pulse);
+                               }
+                               meter->set_beat (b_bbt);
                                meter->set_pulse (pulse);
+
                        } else {
+                               /* MusicTime */
                                double pulse = 0.0;
+                               pair<double, BBT_Time> b_bbt;
                                if (prev_m) {
-                                       pulse = prev_m->pulse() + (meter->beat() - prev_m->beat()) / prev_m->note_divisor();
+                                       const double beats = (meter->bbt().bars - prev_m->bbt().bars) * prev_m->divisions_per_bar();
+                                       if (beats + prev_m->beat() != meter->beat()) {
+                                               /* reordering caused a bbt change */
+                                               b_bbt = make_pair (beats + prev_m->beat()
+                                                                  , BBT_Time ((beats / prev_m->divisions_per_bar()) + prev_m->bbt().bars, 1, 0));
+                                       } else {
+                                               b_bbt = make_pair (beats + prev_m->beat(), meter->bbt());
+                                       }
+                                       pulse = (beats / prev_m->note_divisor()) + prev_m->pulse();
                                } else {
+                                       /* shouldn't happen - the first is audio-locked */
                                        pulse = pulse_at_beat_locked (metrics, meter->beat());
+                                       b_bbt = make_pair (meter->beat(), meter->bbt());
                                }
-                               meter->set_frame (frame_at_pulse_locked (metrics, pulse));
+
+                               meter->set_beat (b_bbt);
                                meter->set_pulse (pulse);
+                               meter->set_frame (frame_at_pulse_locked (metrics, pulse));
                        }
 
                        prev_m = meter;
@@ -1504,68 +1324,11 @@ TempoMap::recompute_map (Metrics& metrics, framepos_t end)
        recompute_meters (metrics);
 }
 
-double
-TempoMap::pulse_at_beat (const double& beat) const
+TempoMetric
+TempoMap::metric_at (framepos_t frame, Metrics::const_iterator* last) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       return pulse_at_beat_locked (_metrics, beat);
-}
-
-double
-TempoMap::pulse_at_beat_locked (const Metrics& metrics, const double& beat) const
-{
-       MeterSection* prev_ms = 0;
-       double accumulated_beats = 0.0;
-
-       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
-               MeterSection* m;
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (prev_ms && m->beat() > beat) {
-                               break;
-                       }
-                       accumulated_beats = m->beat();
-                       prev_ms = m;
-               }
-
-       }
-       double const ret = prev_ms->pulse() + ((beat - accumulated_beats) / prev_ms->note_divisor());
-       return ret;
-}
-
-double
-TempoMap::beat_at_pulse (const double& pulse) const
-{
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       return beat_at_pulse_locked (_metrics, pulse);
-}
-
-double
-TempoMap::beat_at_pulse_locked (const Metrics& metrics, const double& pulse) const
-{
-       MeterSection* prev_ms = 0;
-       double accumulated_beats = 0.0;
-
-       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
-               MeterSection* m;
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (prev_ms && m->pulse() > pulse) {
-                               break;
-                       }
-                       accumulated_beats = m->beat();
-                       prev_ms = m;
-               }
-       }
-
-       double const beats_in_section = (pulse - prev_ms->pulse()) * prev_ms->note_divisor();
-
-       return beats_in_section + accumulated_beats;
-}
-
-TempoMetric
-TempoMap::metric_at (framepos_t frame, Metrics::const_iterator* last) const
-{
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       TempoMetric m (first_meter(), first_tempo());
+       TempoMetric m (first_meter(), first_tempo());
 
        /* at this point, we are *guaranteed* to have m.meter and m.tempo pointing
           at something, because we insert the default tempo and meter during
@@ -1620,211 +1383,215 @@ TempoMap::metric_at (BBT_Time bbt) const
        return m;
 }
 
-void
-TempoMap::bbt_time (framepos_t frame, BBT_Time& bbt)
-{
-
-       if (frame < 0) {
-               bbt.bars = 1;
-               bbt.beats = 1;
-               bbt.ticks = 0;
-               warning << string_compose (_("tempo map asked for BBT time at frame %1\n"), frame) << endmsg;
-               return;
-       }
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       double const beat = beat_at_frame_locked (_metrics, frame);
-
-       bbt = beats_to_bbt_locked (_metrics, beat);
-}
-
 double
-TempoMap::bbt_to_beats (const Timecode::BBT_Time& bbt)
+TempoMap::beat_at_frame (const framecnt_t& frame) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-
-       return bbt_to_beats_locked (_metrics, bbt);
+       return beat_at_frame_locked (_metrics, frame);
 }
 
+/* meter / tempo section based */
 double
-TempoMap::bbt_to_beats_locked (const Metrics& metrics, const Timecode::BBT_Time& bbt) const
+TempoMap::beat_at_frame_locked (const Metrics& metrics, const framecnt_t& frame) const
 {
-       /* CALLER HOLDS READ LOCK */
+       const TempoSection& ts = tempo_section_at_frame_locked (metrics, frame);
+       MeterSection* prev_m = 0;
+       MeterSection* next_m = 0;
 
-       double accumulated_beats = 0.0;
-       double accumulated_bars = 0.0;
-       MeterSection* prev_ms = 0;
-       /* because audio-locked meters have 'fake' integral beats,
-          there is no pulse offset here.
-       */
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                MeterSection* m;
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       double bars_to_m = 0.0;
-                       if (prev_ms) {
-                               bars_to_m = (m->beat() - prev_ms->beat()) / prev_ms->divisions_per_bar();
-                               if ((bars_to_m + accumulated_bars) > (bbt.bars - 1)) {
-                                       break;
-                               }
-                               accumulated_beats = m->beat();
-                               accumulated_bars += bars_to_m;
+                       if (prev_m && m->frame() > frame) {
+                               next_m = m;
+                               break;
                        }
-                       prev_ms = m;
+                       prev_m = m;
                }
        }
+       if (frame < prev_m->frame()) {
+               return 0.0;
+       }
+       const double beat = prev_m->beat() + (ts.pulse_at_frame (frame, _frame_rate) - prev_m->pulse()) * prev_m->note_divisor();
 
-       double const remaining_bars = (bbt.bars - 1) - accumulated_bars;
-       double const remaining_bars_in_beats = remaining_bars * prev_ms->divisions_per_bar();
-       double const ret = remaining_bars_in_beats + accumulated_beats + (bbt.beats - 1) + (bbt.ticks / BBT_Time::ticks_per_beat);
+       /* audio locked meters fake their beat */
+       if (next_m && next_m->beat() < beat) {
+               return next_m->beat();
+       }
 
-       return ret;
+       return beat;
 }
 
-Timecode::BBT_Time
-TempoMap::beats_to_bbt (const double& beats)
+framecnt_t
+TempoMap::frame_at_beat (const double& beat) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-
-       return beats_to_bbt_locked (_metrics, beats);
+       return frame_at_beat_locked (_metrics, beat);
 }
 
-Timecode::BBT_Time
-TempoMap::beats_to_bbt_locked (const Metrics& metrics, const double& b) const
+/* meter section based */
+framecnt_t
+TempoMap::frame_at_beat_locked (const Metrics& metrics, const double& beat) const
 {
-       /* CALLER HOLDS READ LOCK */
-       MeterSection* prev_ms = 0;
-       const double beats = (b < 0.0) ? 0.0 : b;
-       uint32_t accumulated_bars = 0;
-       double accumulated_beats = 0.0;
+       const TempoSection* prev_t = &tempo_section_at_beat_locked (metrics, beat);
+       const MeterSection* prev_m = &meter_section_at_beat_locked (metrics, beat);
 
-       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
-               MeterSection* m = 0;
+       return prev_t->frame_at_pulse (((beat - prev_m->beat()) / prev_m->note_divisor()) + prev_m->pulse(), _frame_rate);
+}
 
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+Tempo
+TempoMap::tempo_at_frame (const framepos_t& frame) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return tempo_at_frame_locked (_metrics, frame);
+}
 
-                       if (prev_ms) {
-                               double const beats_to_m = m->beat() - prev_ms->beat();
-                               if (accumulated_beats + beats_to_m > beats) {
-                                       /* this is the meter after the one our beat is on*/
-                                       break;
-                               }
+Tempo
+TempoMap::tempo_at_frame_locked (const Metrics& metrics, const framepos_t& frame) const
+{
+       TempoSection* prev_t = 0;
 
-                               /* we need a whole number of bars. */
-                               accumulated_bars += (beats_to_m + 1) / prev_ms->divisions_per_bar();
-                               accumulated_beats += beats_to_m;
+       for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+               TempoSection* t;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
                        }
-
-                       prev_ms = m;
+                       if ((prev_t) && t->frame() > frame) {
+                               /* t is the section past frame */
+                               const double ret_bpm = prev_t->tempo_at_frame (frame, _frame_rate) * prev_t->note_type();
+                               const Tempo ret_tempo (ret_bpm, prev_t->note_type());
+                               return ret_tempo;
+                       }
+                       prev_t = t;
                }
        }
 
-       double const beats_in_ms = beats - accumulated_beats;
-       uint32_t const bars_in_ms = (uint32_t) floor (beats_in_ms / prev_ms->divisions_per_bar());
-       uint32_t const total_bars = bars_in_ms + accumulated_bars;
-       double const remaining_beats = beats_in_ms - (bars_in_ms * prev_ms->divisions_per_bar());
-       double const remaining_ticks = (remaining_beats - floor (remaining_beats)) * BBT_Time::ticks_per_beat;
+       const double ret = prev_t->beats_per_minute();
+       const Tempo ret_tempo (ret, prev_t->note_type ());
 
-       BBT_Time ret;
+       return ret_tempo;
+}
 
-       ret.ticks = (uint32_t) floor (remaining_ticks + 0.5);
-       ret.beats = (uint32_t) floor (remaining_beats);
-       ret.bars = total_bars;
+/** returns the frame at which the supplied tempo occurs, or
+ *  the frame of the last tempo section (search exhausted)
+ *  only the position of the first occurence will be returned
+ *  (extend me)
+*/
+framepos_t
+TempoMap::frame_at_tempo (const Tempo& tempo) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return frame_at_tempo_locked (_metrics, tempo);
+}
 
-       /* 0 0 0 to 1 1 0 - based mapping*/
-       ++ret.bars;
-       ++ret.beats;
 
-       if (ret.ticks >= BBT_Time::ticks_per_beat) {
-               ++ret.beats;
-               ret.ticks -= BBT_Time::ticks_per_beat;
-       }
+framepos_t
+TempoMap::frame_at_tempo_locked (const Metrics& metrics, const Tempo& tempo) const
+{
+       TempoSection* prev_t = 0;
+       const double tempo_ppm = tempo.beats_per_minute() / tempo.note_type();
 
-       if (ret.beats >= prev_ms->divisions_per_bar() + 1) {
-               ++ret.bars;
-               ret.beats = 1;
-       }
+       Metrics::const_iterator i;
 
-       return ret;
-}
+       for (i = _metrics.begin(); i != _metrics.end(); ++i) {
+               TempoSection* t;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
 
-Timecode::BBT_Time
-TempoMap::pulse_to_bbt (const double& pulse)
-{
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       MeterSection* prev_ms = 0;
-       uint32_t accumulated_bars = 0;
-       double accumulated_pulses = 0.0;
+                       if (!t->active()) {
+                               continue;
+                       }
 
-       for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
-               MeterSection* m = 0;
+                       const double t_ppm = t->beats_per_minute() / t->note_type();
 
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (t_ppm == tempo_ppm) {
+                               return t->frame();
+                       }
 
-                       if (prev_ms) {
-                               double const pulses_to_m = m->pulse() - prev_ms->pulse();
-                               if (accumulated_pulses + pulses_to_m > pulse) {
-                                       /* this is the meter after the one our beat is on*/
-                                       break;
-                               }
+                       if (prev_t) {
+                               const double prev_t_ppm = prev_t->beats_per_minute() / prev_t->note_type();
 
-                               /* we need a whole number of bars. */
-                               accumulated_pulses += pulses_to_m;
-                               accumulated_bars += ((pulses_to_m * prev_ms->note_divisor()) + 1) / prev_ms->divisions_per_bar();
+                               if ((t_ppm > tempo_ppm && prev_t_ppm < tempo_ppm) || (t_ppm < tempo_ppm && prev_t_ppm > tempo_ppm)) {
+                                       const framepos_t ret_frame = prev_t->frame_at_tempo (tempo_ppm, prev_t->pulse(), _frame_rate);
+                                       return ret_frame;
+                               }
                        }
-
-                       prev_ms = m;
+                       prev_t = t;
                }
        }
-       double const beats_in_ms = (pulse - prev_ms->pulse()) * prev_ms->note_divisor();
-       uint32_t const bars_in_ms = (uint32_t) floor (beats_in_ms / prev_ms->divisions_per_bar());
-       uint32_t const total_bars = bars_in_ms + accumulated_bars;
-       double const remaining_beats = beats_in_ms - (bars_in_ms * prev_ms->divisions_per_bar());
-       double const remaining_ticks = (remaining_beats - floor (remaining_beats)) * BBT_Time::ticks_per_beat;
 
-       BBT_Time ret;
+       return prev_t->frame();
+}
 
-       ret.ticks = (uint32_t) floor (remaining_ticks + 0.5);
-       ret.beats = (uint32_t) floor (remaining_beats);
-       ret.bars = total_bars;
+/** more precise than doing tempo_at_frame (frame_at_beat (b)),
+ *  as there is no intermediate frame rounding.
+ */
+Tempo
+TempoMap::tempo_at_beat (const double& beat) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       const MeterSection* prev_m = &meter_section_at_beat_locked (_metrics, beat);
+       const TempoSection* prev_t = &tempo_section_at_beat_locked (_metrics, beat);
+       const double note_type = prev_t->note_type();
 
-       /* 0 0 0 to 1 1 0 mapping*/
-       ++ret.bars;
-       ++ret.beats;
+       return Tempo (prev_t->tempo_at_pulse (((beat - prev_m->beat()) / prev_m->note_divisor()) + prev_m->pulse()) * note_type, note_type);
+}
 
-       if (ret.ticks >= BBT_Time::ticks_per_beat) {
-               ++ret.beats;
-               ret.ticks -= BBT_Time::ticks_per_beat;
-       }
+double
+TempoMap::pulse_at_beat (const double& beat) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return pulse_at_beat_locked (_metrics, beat);
+}
 
-       if (ret.beats >= prev_ms->divisions_per_bar() + 1) {
-               ++ret.bars;
-               ret.beats = 1;
-       }
+double
+TempoMap::pulse_at_beat_locked (const Metrics& metrics, const double& beat) const
+{
+       const MeterSection* prev_m = &meter_section_at_beat_locked (metrics, beat);
 
-       return ret;
+       return prev_m->pulse() + ((beat - prev_m->beat()) / prev_m->note_divisor());
 }
 
 double
-TempoMap::beat_at_frame (const framecnt_t& frame) const
+TempoMap::beat_at_pulse (const double& pulse) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       return beat_at_frame_locked (_metrics, frame);
+       return beat_at_pulse_locked (_metrics, pulse);
 }
 
 double
-TempoMap::beat_at_frame_locked (const Metrics& metrics, const framecnt_t& frame) const
+TempoMap::beat_at_pulse_locked (const Metrics& metrics, const double& pulse) const
 {
-       framecnt_t const offset_frame = frame + frame_offset_at (metrics, frame);
-       double const pulse = pulse_at_frame_locked (metrics, offset_frame);
+       MeterSection* prev_m = 0;
+
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               MeterSection* m;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (prev_m && m->pulse() > pulse) {
+                               if (((pulse - prev_m->pulse()) * prev_m->note_divisor()) + prev_m->beat() > m->beat()) {
+                                       break;
+                               }
+                       }
+                       prev_m = m;
+               }
+       }
 
-       return beat_at_pulse_locked (metrics, pulse);
+       double const ret = ((pulse - prev_m->pulse()) * prev_m->note_divisor()) + prev_m->beat();
+       return ret;
+}
+
+double
+TempoMap::pulse_at_frame (const framecnt_t& frame) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return pulse_at_frame_locked (_metrics, frame);
 }
 
+/* tempo section based */
 double
 TempoMap::pulse_at_frame_locked (const Metrics& metrics, const framecnt_t& frame) const
 {
        /* HOLD (at least) THE READER LOCK */
-       TempoSection* prev_ts = 0;
-       double accumulated_pulses = 0.0;
+       TempoSection* prev_t = 0;
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
@@ -1832,44 +1599,35 @@ TempoMap::pulse_at_frame_locked (const Metrics& metrics, const framecnt_t& frame
                        if (!t->active()) {
                                continue;
                        }
-                       if (prev_ts && t->frame() > frame) {
+                       if (prev_t && t->frame() > frame) {
                                /*the previous ts is the one containing the frame */
-                               double const ret = prev_ts->pulse_at_frame (frame, _frame_rate);
+                               const double ret = prev_t->pulse_at_frame (frame, _frame_rate);
                                return ret;
                        }
-                       accumulated_pulses = t->pulse();
-                       prev_ts = t;
+                       prev_t = t;
                }
        }
 
        /* treated as constant for this ts */
-       double const pulses_in_section = (frame - prev_ts->frame()) / prev_ts->frames_per_pulse (_frame_rate);
+       const double pulses_in_section = (frame - prev_t->frame()) / prev_t->frames_per_pulse (_frame_rate);
 
-       return pulses_in_section + accumulated_pulses;
+       return pulses_in_section + prev_t->pulse();
 }
 
 framecnt_t
-TempoMap::frame_at_beat (const double& beat) const
+TempoMap::frame_at_pulse (const double& pulse) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       return frame_at_beat_locked (_metrics, beat);
-}
-
-framecnt_t
-TempoMap::frame_at_beat_locked (const Metrics& metrics, const double& beat) const
-{
-       framecnt_t const frame = frame_at_pulse_locked (metrics, pulse_at_beat_locked (metrics, beat));
-       frameoffset_t const frame_off = frame_offset_at (metrics, frame);
-       return frame - frame_off;
+       return frame_at_pulse_locked (_metrics, pulse);
 }
 
+/* tempo section based */
 framecnt_t
 TempoMap::frame_at_pulse_locked (const Metrics& metrics, const double& pulse) const
 {
        /* HOLD THE READER LOCK */
 
-       const TempoSection* prev_ts = 0;
-       double accumulated_pulses = 0.0;
+       const TempoSection* prev_t = 0;
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
@@ -1878,147 +1636,385 @@ TempoMap::frame_at_pulse_locked (const Metrics& metrics, const double& pulse) co
                        if (!t->active()) {
                                continue;
                        }
-                       if (prev_ts && t->pulse() > pulse) {
-                               return prev_ts->frame_at_pulse (pulse, _frame_rate);
+                       if (prev_t && t->pulse() > pulse) {
+                               return prev_t->frame_at_pulse (pulse, _frame_rate);
                        }
 
-                       accumulated_pulses = t->pulse();
-                       prev_ts = t;
+                       prev_t = t;
                }
        }
        /* must be treated as constant, irrespective of _type */
-       double const pulses_in_section = pulse - accumulated_pulses;
-       double const dtime = pulses_in_section * prev_ts->frames_per_pulse (_frame_rate);
+       double const pulses_in_section = pulse - prev_t->pulse();
+       double const dtime = pulses_in_section * prev_t->frames_per_pulse (_frame_rate);
 
-       framecnt_t const ret = (framecnt_t) floor (dtime) + prev_ts->frame();
+       framecnt_t const ret = (framecnt_t) floor (dtime) + prev_t->frame();
 
        return ret;
 }
 
 double
-TempoMap::beat_offset_at (const Metrics& metrics, const double& beat) const
+TempoMap::beat_at_bbt (const Timecode::BBT_Time& bbt)
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return beat_at_bbt_locked (_metrics, bbt);
+}
+
+
+double
+TempoMap::beat_at_bbt_locked (const Metrics& metrics, const Timecode::BBT_Time& bbt) const
 {
+       /* CALLER HOLDS READ LOCK */
+
        MeterSection* prev_m = 0;
-       double beat_off = first_meter().pulse();
 
+       /* because audio-locked meters have 'fake' integral beats,
+          there is no pulse offset here.
+       */
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
-               MeterSection* m = 0;
+               MeterSection* m;
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
                        if (prev_m) {
-                               if (m->beat() > beat) {
+                               const double bars_to_m = (m->beat() - prev_m->beat()) / prev_m->divisions_per_bar();
+                               if ((bars_to_m + (prev_m->bbt().bars - 1)) > (bbt.bars - 1)) {
                                        break;
                                }
-
-                               if (m->position_lock_style() == AudioTime) {
-                                       beat_off += ((m->beat() - prev_m->beat()) / prev_m->note_divisor()) - floor (m->pulse() - prev_m->pulse());
-                               }
                        }
                        prev_m = m;
                }
        }
 
-       return beat_off;
+       const double remaining_bars = bbt.bars - prev_m->bbt().bars;
+       const double remaining_bars_in_beats = remaining_bars * prev_m->divisions_per_bar();
+       const double ret = remaining_bars_in_beats + prev_m->beat() + (bbt.beats - 1) + (bbt.ticks / BBT_Time::ticks_per_beat);
+
+       return ret;
+}
+
+Timecode::BBT_Time
+TempoMap::bbt_at_beat (const double& beats)
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return bbt_at_beat_locked (_metrics, beats);
 }
 
-frameoffset_t
-TempoMap::frame_offset_at (const Metrics& metrics, const framepos_t& frame) const
+Timecode::BBT_Time
+TempoMap::bbt_at_beat_locked (const Metrics& metrics, const double& b) const
 {
-       frameoffset_t frame_off = 0;
+       /* CALLER HOLDS READ LOCK */
        MeterSection* prev_m = 0;
+       const double beats = max (0.0, b);
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                MeterSection* m = 0;
+
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (m->frame() > frame) {
-                               break;
-                       }
-                       if (prev_m && m->position_lock_style() == AudioTime) {
-                               const double pulse = prev_m->pulse() + ((m->beat() - prev_m->beat()) / prev_m->note_divisor());
-                               frame_off += frame_at_pulse_locked (metrics, pulse) - m->frame();
+                       if (prev_m) {
+                               if (m->beat() > beats) {
+                                       /* this is the meter after the one our beat is on*/
+                                       break;
+                               }
                        }
+
                        prev_m = m;
                }
        }
 
-       return frame_off;
-}
+       const double beats_in_ms = beats - prev_m->beat();
+       const uint32_t bars_in_ms = (uint32_t) floor (beats_in_ms / prev_m->divisions_per_bar());
+       const uint32_t total_bars = bars_in_ms + (prev_m->bbt().bars - 1);
+       const double remaining_beats = beats_in_ms - (bars_in_ms * prev_m->divisions_per_bar());
+       const double remaining_ticks = (remaining_beats - floor (remaining_beats)) * BBT_Time::ticks_per_beat;
 
-framepos_t
-TempoMap::frame_time (const BBT_Time& bbt)
-{
-       if (bbt.bars < 1) {
-               warning << string_compose (_("tempo map asked for frame time at bar < 1  (%1)\n"), bbt) << endmsg;
-               return 0;
-       }
+       BBT_Time ret;
 
-       if (bbt.beats < 1) {
-               throw std::logic_error ("beats are counted from one");
-       }
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       double const beat = bbt_to_beats_locked (_metrics, bbt);
-       framecnt_t const frame = frame_at_beat_locked (_metrics, beat);
-       return frame;
-}
+       ret.ticks = (uint32_t) floor (remaining_ticks + 0.5);
+       ret.beats = (uint32_t) floor (remaining_beats);
+       ret.bars = total_bars;
 
-framepos_t
-TempoMap::frame_time_locked (const Metrics& metrics, const BBT_Time& bbt) const
-{
-       /* HOLD THE READER LOCK */
+       /* 0 0 0 to 1 1 0 - based mapping*/
+       ++ret.bars;
+       ++ret.beats;
+
+       if (ret.ticks >= BBT_Time::ticks_per_beat) {
+               ++ret.beats;
+               ret.ticks -= BBT_Time::ticks_per_beat;
+       }
+
+       if (ret.beats >= prev_m->divisions_per_bar() + 1) {
+               ++ret.bars;
+               ret.beats = 1;
+       }
+
+       return ret;
+}
+
+double
+TempoMap::pulse_at_bbt (const Timecode::BBT_Time& bbt)
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       return pulse_at_bbt_locked (_metrics, bbt);
+}
+
+double
+TempoMap::pulse_at_bbt_locked (const Metrics& metrics, const Timecode::BBT_Time& bbt) const
+{
+       /* CALLER HOLDS READ LOCK */
+
+       MeterSection* prev_m = 0;
+
+       /* because audio-locked meters have 'fake' integral beats,
+          there is no pulse offset here.
+       */
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               MeterSection* m;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (prev_m) {
+                               if (m->bbt().bars > bbt.bars) {
+                                       break;
+                               }
+                       }
+                       prev_m = m;
+               }
+       }
+
+       const double remaining_bars = bbt.bars - prev_m->bbt().bars;
+       const double remaining_pulses = remaining_bars * prev_m->divisions_per_bar() / prev_m->note_divisor();
+       const double ret = remaining_pulses + prev_m->pulse() + (((bbt.beats - 1) + (bbt.ticks / BBT_Time::ticks_per_beat)) / prev_m->note_divisor());
+
+       return ret;
+}
+
+Timecode::BBT_Time
+TempoMap::bbt_at_pulse (const double& pulse)
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       return bbt_at_pulse_locked (_metrics, pulse);
+}
+
+Timecode::BBT_Time
+TempoMap::bbt_at_pulse_locked (const Metrics& metrics, const double& pulse) const
+{
+       MeterSection* prev_m = 0;
+
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               MeterSection* m = 0;
+
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+
+                       if (prev_m) {
+                               double const pulses_to_m = m->pulse() - prev_m->pulse();
+                               if (prev_m->pulse() + pulses_to_m > pulse) {
+                                       /* this is the meter after the one our beat is on*/
+                                       break;
+                               }
+                       }
+
+                       prev_m = m;
+               }
+       }
+
+       const double beats_in_ms = (pulse - prev_m->pulse()) * prev_m->note_divisor();
+       const uint32_t bars_in_ms = (uint32_t) floor (beats_in_ms / prev_m->divisions_per_bar());
+       const uint32_t total_bars = bars_in_ms + (prev_m->bbt().bars - 1);
+       const double remaining_beats = beats_in_ms - (bars_in_ms * prev_m->divisions_per_bar());
+       const double remaining_ticks = (remaining_beats - floor (remaining_beats)) * BBT_Time::ticks_per_beat;
 
-       framepos_t const ret = frame_at_pulse_locked (metrics, pulse_at_beat_locked (metrics, bbt_to_beats_locked (metrics, bbt)));
+       BBT_Time ret;
+
+       ret.ticks = (uint32_t) floor (remaining_ticks + 0.5);
+       ret.beats = (uint32_t) floor (remaining_beats);
+       ret.bars = total_bars;
+
+       /* 0 0 0 to 1 1 0 mapping*/
+       ++ret.bars;
+       ++ret.beats;
+
+       if (ret.ticks >= BBT_Time::ticks_per_beat) {
+               ++ret.beats;
+               ret.ticks -= BBT_Time::ticks_per_beat;
+       }
+
+       if (ret.beats >= prev_m->divisions_per_bar() + 1) {
+               ++ret.bars;
+               ret.beats = 1;
+       }
 
        return ret;
 }
 
+BBT_Time
+TempoMap::bbt_at_frame (framepos_t frame)
+{
+       if (frame < 0) {
+               BBT_Time bbt;
+               bbt.bars = 1;
+               bbt.beats = 1;
+               bbt.ticks = 0;
+               warning << string_compose (_("tempo map asked for BBT time at frame %1\n"), frame) << endmsg;
+               return bbt;
+       }
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       return bbt_at_frame_locked (_metrics, frame);
+}
+
+BBT_Time
+TempoMap::bbt_at_frame_rt (framepos_t frame)
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock, Glib::Threads::TRY_LOCK);
+
+       if (!lm.locked()) {
+               throw std::logic_error ("TempoMap::bbt_time_rt() could not lock tempo map");
+       }
+
+       return bbt_at_frame_locked (_metrics, frame);
+}
+
+Timecode::BBT_Time
+TempoMap::bbt_at_frame_locked (const Metrics& metrics, const framepos_t& frame) const
+{
+       if (frame < 0) {
+               BBT_Time bbt;
+               bbt.bars = 1;
+               bbt.beats = 1;
+               bbt.ticks = 0;
+               warning << string_compose (_("tempo map asked for BBT time at frame %1\n"), frame) << endmsg;
+               return bbt;
+       }
+       const double beat = beat_at_frame_locked (metrics, frame);
+
+       return bbt_at_beat_locked (metrics, beat);
+}
+
+framepos_t
+TempoMap::frame_at_bbt (const BBT_Time& bbt)
+{
+       if (bbt.bars < 1) {
+               warning << string_compose (_("tempo map asked for frame time at bar < 1  (%1)\n"), bbt) << endmsg;
+               return 0;
+       }
+
+       if (bbt.beats < 1) {
+               throw std::logic_error ("beats are counted from one");
+       }
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       return frame_at_bbt_locked (_metrics, bbt);
+}
+
+/* meter & tempo section based */
+framepos_t
+TempoMap::frame_at_bbt_locked (const Metrics& metrics, const BBT_Time& bbt) const
+{
+       /* HOLD THE READER LOCK */
+
+       const framepos_t ret = frame_at_beat_locked (metrics, beat_at_bbt_locked (metrics, bbt));
+       return ret;
+}
+
 bool
-TempoMap::check_solved (Metrics& metrics, bool by_frame)
+TempoMap::check_solved (const Metrics& metrics) const
 {
-       TempoSection* prev_ts = 0;
+       TempoSection* prev_t = 0;
+       MeterSection* prev_m = 0;
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
+               MeterSection* m;
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
                        if (!t->active()) {
                                continue;
                        }
-                       if (prev_ts) {
-                               if ((by_frame && t->frame() < prev_ts->frame()) || (!by_frame && t->pulse() < prev_ts->pulse())) {
+                       if (prev_t) {
+                               /* check ordering */
+                               if ((t->frame() <= prev_t->frame()) || (t->pulse() <= prev_t->pulse())) {
                                        return false;
                                }
-                               /* precision check ensures pulses and frames align independent of lock style.*/
-                               if (by_frame && t->frame() != prev_ts->frame_at_pulse (t->pulse(), _frame_rate)) {
+
+                               /* precision check ensures tempo and frames align.*/
+                               if (t->frame() != prev_t->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate)) {
+                                       if (!t->locked_to_meter()) {
+                                               return false;
+                                       }
+                               }
+
+                               /* gradient limit - who knows what it should be?
+                                  things are also ok (if a little chaotic) without this
+                               */
+                               if (fabs (prev_t->c_func()) > 1000.0) {
+                                       //std::cout << "c : " << prev_t->c_func() << std::endl;
+                                       return false;
+                               }
+                       }
+                       prev_t = t;
+               }
+
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (prev_m && m->position_lock_style() == AudioTime) {
+                               TempoSection* t = const_cast<TempoSection*>(&tempo_section_at_frame_locked (metrics, m->frame() - 1));
+                               const double nascent_m_pulse = ((m->beat() - prev_m->beat()) / prev_m->note_divisor()) + prev_m->pulse();
+                               const framepos_t nascent_m_frame = t->frame_at_pulse (nascent_m_pulse, _frame_rate);
+
+                               if (t && (nascent_m_frame > m->frame() || nascent_m_frame < 0)) {
                                        return false;
                                }
                        }
-                       prev_ts = t;
+
+                       prev_m = m;
                }
+
        }
 
        return true;
 }
 
 bool
-TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm, const framepos_t& frame)
+TempoMap::set_active_tempos (const Metrics& metrics, const framepos_t& frame)
 {
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               TempoSection* t;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->movable()) {
+                               t->set_active (true);
+                               continue;
+                       }
+                       if (t->movable() && t->active () && t->position_lock_style() == AudioTime && t->frame() < frame) {
+                               t->set_active (false);
+                               t->set_pulse (0.0);
+                       } else if (t->movable() && t->position_lock_style() == AudioTime && t->frame() > frame) {
+                               t->set_active (true);
+                       } else if (t->movable() && t->position_lock_style() == AudioTime && t->frame() == frame) {
+                               return false;
+                       }
+               }
+       }
+       return true;
+}
 
-       TempoSection* prev_ts = 0;
+bool
+TempoMap::solve_map_frame (Metrics& imaginary, TempoSection* section, const framepos_t& frame)
+{
+       TempoSection* prev_t = 0;
        TempoSection* section_prev = 0;
-       MetricSectionFrameSorter fcmp;
-       MetricSectionSorter cmp;
        framepos_t first_m_frame = 0;
+
+       /* can't move a tempo before the first meter */
        for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
                MeterSection* m;
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
                        if (!m->movable()) {
                                first_m_frame = m->frame();
+                               break;
                        }
                }
        }
        if (section->movable() && frame <= first_m_frame) {
                return false;
-       } else {
-               section->set_active (true);
        }
+
+       section->set_active (true);
        section->set_frame (frame);
 
        for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
@@ -2028,80 +2024,61 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                        if (!t->active()) {
                                continue;
                        }
-                       if (prev_ts) {
+                       if (prev_t) {
                                if (t == section) {
-                                       section_prev = prev_ts;
+                                       section_prev = prev_t;
+                                       if (t->locked_to_meter()) {
+                                               prev_t = t;
+                                       }
                                        continue;
                                }
                                if (t->position_lock_style() == MusicTime) {
-                                       prev_ts->set_c_func (prev_ts->compute_c_func_pulse (t->pulses_per_minute(), t->pulse(), _frame_rate));
-                                       t->set_frame (prev_ts->frame_at_pulse (t->pulse(), _frame_rate));
+                                       prev_t->set_c_func (prev_t->compute_c_func_pulse (t->pulses_per_minute(), t->pulse(), _frame_rate));
+                                       t->set_frame (prev_t->frame_at_pulse (t->pulse(), _frame_rate));
                                } else {
-                                       prev_ts->set_c_func (prev_ts->compute_c_func_frame (t->pulses_per_minute(), t->frame(), _frame_rate));
-                                       t->set_pulse (prev_ts->pulse_at_frame (t->frame(), _frame_rate));
+                                       prev_t->set_c_func (prev_t->compute_c_func_frame (t->pulses_per_minute(), t->frame(), _frame_rate));
+                                       if (!t->locked_to_meter()) {
+                                               t->set_pulse (prev_t->pulse_at_frame (t->frame(), _frame_rate));
+                                       }
                                }
                        }
-                       prev_ts = t;
+                       prev_t = t;
                }
        }
 
        if (section_prev) {
                section_prev->set_c_func (section_prev->compute_c_func_frame (section->pulses_per_minute(), frame, _frame_rate));
-               section->set_pulse (section_prev->pulse_at_frame (frame, _frame_rate));
+               if (!section->locked_to_meter()) {
+                       section->set_pulse (section_prev->pulse_at_frame (frame, _frame_rate));
+               }
        }
 
-       if (section->position_lock_style() == MusicTime) {
-               /* we're setting the frame */
-               section->set_position_lock_style (AudioTime);
-               recompute_tempos (imaginary);
-               section->set_position_lock_style (MusicTime);
-       } else {
-               recompute_tempos (imaginary);
-       }
+#if (0)
+       recompute_tempos (imaginary);
 
-       if (check_solved (imaginary, true)) {
-               recompute_meters (imaginary);
+       if (check_solved (imaginary)) {
                return true;
+       } else {
+               dunp (imaginary, std::cout);
        }
+#endif
 
+       MetricSectionFrameSorter fcmp;
        imaginary.sort (fcmp);
-       if (section->position_lock_style() == MusicTime) {
-               /* we're setting the frame */
-               section->set_position_lock_style (AudioTime);
-               recompute_tempos (imaginary);
-               section->set_position_lock_style (MusicTime);
-       } else {
-               recompute_tempos (imaginary);
-       }
-       if (check_solved (imaginary, true)) {
-               recompute_meters (imaginary);
-               return true;
-       }
 
-       imaginary.sort (cmp);
-       if (section->position_lock_style() == MusicTime) {
-               /* we're setting the frame */
-               section->set_position_lock_style (AudioTime);
-               recompute_tempos (imaginary);
-               section->set_position_lock_style (MusicTime);
-       } else {
-               recompute_tempos (imaginary);
-       }
-       if (check_solved (imaginary, true)) {
-               recompute_meters (imaginary);
+       recompute_tempos (imaginary);
+
+       if (check_solved (imaginary)) {
                return true;
        }
-       //dump (imaginary, std::cerr);
 
        return false;
 }
 
 bool
-TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm, const double& pulse)
+TempoMap::solve_map_pulse (Metrics& imaginary, TempoSection* section, const double& pulse)
 {
-       MetricSectionSorter cmp;
-       MetricSectionFrameSorter fcmp;
-       TempoSection* prev_ts = 0;
+       TempoSection* prev_t = 0;
        TempoSection* section_prev = 0;
 
        section->set_pulse (pulse);
@@ -2112,222 +2089,711 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                        if (!t->active()) {
                                continue;
                        }
-                       if (prev_ts) {
+                       if (!t->movable()) {
+                               t->set_pulse (0.0);
+                               prev_t = t;
+                               continue;
+                       }
+                       if (prev_t) {
                                if (t == section) {
-                                       section_prev = prev_ts;
+                                       section_prev = prev_t;
                                        continue;
                                }
                                if (t->position_lock_style() == MusicTime) {
-                                       prev_ts->set_c_func (prev_ts->compute_c_func_pulse (t->pulses_per_minute(), t->pulse(), _frame_rate));
-                                       t->set_frame (prev_ts->frame_at_pulse (t->pulse(), _frame_rate));
+                                       prev_t->set_c_func (prev_t->compute_c_func_pulse (t->pulses_per_minute(), t->pulse(), _frame_rate));
+                                       t->set_frame (prev_t->frame_at_pulse (t->pulse(), _frame_rate));
                                } else {
-                                       prev_ts->set_c_func (prev_ts->compute_c_func_frame (t->pulses_per_minute(), t->frame(), _frame_rate));
-                                       t->set_pulse (prev_ts->pulse_at_frame (t->frame(), _frame_rate));
+                                       prev_t->set_c_func (prev_t->compute_c_func_frame (t->pulses_per_minute(), t->frame(), _frame_rate));
+                                       if (!t->locked_to_meter()) {
+                                               t->set_pulse (prev_t->pulse_at_frame (t->frame(), _frame_rate));
+                                       }
                                }
                        }
-                       prev_ts = t;
+                       prev_t = t;
                }
        }
+
        if (section_prev) {
                section_prev->set_c_func (section_prev->compute_c_func_pulse (section->pulses_per_minute(), pulse, _frame_rate));
                section->set_frame (section_prev->frame_at_pulse (pulse, _frame_rate));
        }
 
-       if (section->position_lock_style() == AudioTime) {
-               /* we're setting the pulse */
-               section->set_position_lock_style (MusicTime);
-               recompute_tempos (imaginary);
-               section->set_position_lock_style (AudioTime);
-       } else {
-               recompute_tempos (imaginary);
-       }
-       if (check_solved (imaginary, false)) {
-               recompute_meters (imaginary);
-               return true;
-       }
+#if (0)
+       recompute_tempos (imaginary);
+
+       if (check_solved (imaginary)) {
+               return true;
+       } else {
+               dunp (imaginary, std::cout);
+       }
+#endif
+
+       MetricSectionSorter cmp;
+       imaginary.sort (cmp);
+
+       recompute_tempos (imaginary);
+       /* Reordering
+        * XX need a restriction here, but only for this case,
+        * as audio locked tempos don't interact in the same way.
+        *
+        * With music-locked tempos, the solution to cross-dragging can fly off the screen
+        * e.g.
+        * |50 bpm                        |250 bpm |60 bpm
+        *                drag 250 to the pulse after 60->
+        * a clue: dragging the second 60 <- past the 250 would cause no such problem.
+        */
+       if (check_solved (imaginary)) {
+               return true;
+       }
+
+       return false;
+}
+
+bool
+TempoMap::solve_map_frame (Metrics& imaginary, MeterSection* section, const framepos_t& frame)
+{
+       /* disallow moving first meter past any subsequent one, and any movable meter before the first one */
+       const MeterSection* other =  &meter_section_at_frame_locked (imaginary, frame);
+       if ((!section->movable() && other->movable()) || (!other->movable() && section->movable() && other->frame() >= frame)) {
+               return false;
+       }
+
+       if (!section->movable()) {
+               /* lock the first tempo to our first meter */
+               if (!set_active_tempos (imaginary, frame)) {
+                       return false;
+               }
+       }
+
+       TempoSection* meter_locked_tempo = 0;
+
+       for (Metrics::const_iterator ii = imaginary.begin(); ii != imaginary.end(); ++ii) {
+               TempoSection* t;
+               if ((t = dynamic_cast<TempoSection*> (*ii)) != 0) {
+                       if ((t->locked_to_meter() || !t->movable()) && t->frame() == section->frame()) {
+                               meter_locked_tempo = t;
+                               break;
+                       }
+               }
+       }
+
+       if (!meter_locked_tempo) {
+               return false;
+       }
+
+       MeterSection* prev_m = 0;
+       Metrics future_map;
+       TempoSection* tempo_copy = copy_metrics_and_point (imaginary, future_map, meter_locked_tempo);
+       bool solved = false;
+
+       for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
+               MeterSection* m;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (m == section){
+                               if (prev_m && section->movable()) {
+                                       const double beats = (pulse_at_frame_locked (imaginary, frame) - prev_m->pulse()) * prev_m->note_divisor();
+                                       if (beats + prev_m->beat() < section->beat()) {
+                                               /* set the frame/pulse corresponding to its musical position,
+                                                * as an earlier time than this has been requested.
+                                               */
+                                               const double new_pulse = ((section->beat() - prev_m->beat())
+                                                                         / prev_m->note_divisor()) + prev_m->pulse();
+
+                                               const framepos_t smallest_frame = frame_at_pulse_locked (future_map, new_pulse);
+
+                                               if ((solved = solve_map_frame (future_map, tempo_copy, smallest_frame))) {
+                                                       meter_locked_tempo->set_pulse (new_pulse);
+                                                       solve_map_frame (imaginary, meter_locked_tempo, smallest_frame);
+                                                       section->set_frame (smallest_frame);
+                                                       section->set_pulse (new_pulse);
+                                               } else {
+                                                       solved = false;
+                                               }
+
+                                               Metrics::const_iterator d = future_map.begin();
+                                               while (d != future_map.end()) {
+                                                       delete (*d);
+                                                       ++d;
+                                               }
+
+                                               if (!solved) {
+                                                       return false;
+                                               }
+                                       } else {
+                                               /* all is ok. set section's locked tempo if allowed.
+                                                  possibly disallowed if there is an adjacent audio-locked tempo.
+                                                  XX this check could possibly go. its never actually happened here.
+                                               */
+                                               MeterSection* meter_copy = const_cast<MeterSection*> (&meter_section_at_frame_locked (future_map, section->frame()));
+                                               meter_copy->set_frame (frame);
+
+                                               if ((solved = solve_map_frame (future_map, tempo_copy, frame))) {
+                                                       section->set_frame (frame);
+                                                       meter_locked_tempo->set_pulse (((section->beat() - prev_m->beat())
+                                                                                               / prev_m->note_divisor()) + prev_m->pulse());
+                                                       solve_map_frame (imaginary, meter_locked_tempo, frame);
+                                               } else {
+                                                       solved = false;
+                                               }
+
+                                               Metrics::const_iterator d = future_map.begin();
+                                               while (d != future_map.end()) {
+                                                       delete (*d);
+                                                       ++d;
+                                               }
+
+                                               if (!solved) {
+                                                       return false;
+                                               }
+                                       }
+                               } else {
+                                       /* not movable (first meter atm) */
+
+                                       tempo_copy->set_frame (frame);
+                                       tempo_copy->set_pulse (0.0);
+
+                                       if ((solved = solve_map_frame (future_map, tempo_copy, frame))) {
+                                               section->set_frame (frame);
+                                               meter_locked_tempo->set_frame (frame);
+                                               meter_locked_tempo->set_pulse (0.0);
+                                               solve_map_frame (imaginary, meter_locked_tempo, frame);
+                                       } else {
+                                               solved = false;
+                                       }
+
+                                       Metrics::const_iterator d = future_map.begin();
+                                       while (d != future_map.end()) {
+                                               delete (*d);
+                                               ++d;
+                                       }
+
+                                       if (!solved) {
+                                               return false;
+                                       }
+
+                                       pair<double, BBT_Time> b_bbt = make_pair (0.0, BBT_Time (1, 1, 0));
+                                       section->set_beat (b_bbt);
+                                       section->set_pulse (0.0);
+
+                               }
+                               break;
+                       }
+
+                       prev_m = m;
+               }
+       }
+
+       MetricSectionFrameSorter fcmp;
+       imaginary.sort (fcmp);
+
+       recompute_meters (imaginary);
+
+       return true;
+}
+
+bool
+TempoMap::solve_map_bbt (Metrics& imaginary, MeterSection* section, const BBT_Time& when)
+{
+       /* disallow setting section to an existing meter's bbt */
+       for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
+               MeterSection* m;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (m != section && m->bbt().bars == when.bars) {
+                               return false;
+                       }
+               }
+       }
+
+       MeterSection* prev_m = 0;
+       MeterSection* section_prev = 0;
+
+       for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
+               MeterSection* m;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       pair<double, BBT_Time> b_bbt;
+                       double new_pulse = 0.0;
+
+                       if (prev_m && m->bbt().bars > when.bars && !section_prev){
+                               section_prev = prev_m;
+                               const double beats = (when.bars - section_prev->bbt().bars) * section_prev->divisions_per_bar();
+                               const double pulse = (beats / section_prev->note_divisor()) + section_prev->pulse();
+                               pair<double, BBT_Time> b_bbt = make_pair (beats + section_prev->beat(), when);
+
+                               section->set_beat (b_bbt);
+                               section->set_pulse (pulse);
+                               section->set_frame (frame_at_pulse_locked (imaginary, pulse));
+                               prev_m = section;
+                               continue;
+                       }
+
+                       if (m->position_lock_style() == AudioTime) {
+                               TempoSection* meter_locked_tempo = 0;
+
+                               for (Metrics::const_iterator ii = imaginary.begin(); ii != imaginary.end(); ++ii) {
+                                       TempoSection* t;
+                                       if ((t = dynamic_cast<TempoSection*> (*ii)) != 0) {
+                                               if ((t->locked_to_meter() || !t->movable()) && t->frame() == m->frame()) {
+                                                       meter_locked_tempo = t;
+                                                       break;
+                                               }
+                                       }
+                               }
+
+                               if (!meter_locked_tempo) {
+                                       return false;
+                               }
+
+                               if (prev_m) {
+                                       const double beats = ((m->bbt().bars - prev_m->bbt().bars) * prev_m->divisions_per_bar());
+
+                                       if (beats + prev_m->beat() != m->beat()) {
+                                               /* tempo/ meter change caused a change in beat (bar). */
+                                               b_bbt = make_pair (beats + prev_m->beat()
+                                                                  , BBT_Time ((beats / prev_m->divisions_per_bar()) + prev_m->bbt().bars, 1, 0));
+                                               new_pulse = prev_m->pulse() + (beats / prev_m->note_divisor());
+                                       } else if (m->movable()) {
+                                               b_bbt = make_pair (m->beat(), m->bbt());
+                                               new_pulse = prev_m->pulse() + (beats / prev_m->note_divisor());
+                                       }
+                               } else {
+                                       b_bbt = make_pair (0.0, BBT_Time (1, 1, 0));
+                               }
+
+                               meter_locked_tempo->set_pulse (new_pulse);
+                               m->set_beat (b_bbt);
+                               m->set_pulse (new_pulse);
+
+                       } else {
+                               /* MusicTime */
+                               const double beats = ((m->bbt().bars - prev_m->bbt().bars) * prev_m->divisions_per_bar());
+                               if (beats + prev_m->beat() != m->beat()) {
+                                       /* tempo/ meter change caused a change in beat (bar). */
+                                       b_bbt = make_pair (beats + prev_m->beat()
+                                                          , BBT_Time ((beats / prev_m->divisions_per_bar()) + prev_m->bbt().bars, 1, 0));
+                               } else {
+                                       b_bbt = make_pair (beats + prev_m->beat()
+                                                          , m->bbt());
+                               }
+                               new_pulse = (beats / prev_m->note_divisor()) + prev_m->pulse();
+                               m->set_beat (b_bbt);
+                               m->set_pulse (new_pulse);
+                               m->set_frame (frame_at_pulse_locked (imaginary, new_pulse));
+                       }
+
+                       prev_m = m;
+               }
+       }
+
+       if (!section_prev) {
+
+               const double beats = (when.bars - prev_m->bbt().bars) * prev_m->divisions_per_bar();
+               const double pulse = (beats / prev_m->note_divisor()) + prev_m->pulse();
+               pair<double, BBT_Time> b_bbt = make_pair (beats + prev_m->beat(), when);
+
+               section->set_beat (b_bbt);
+               section->set_pulse (pulse);
+               section->set_frame (frame_at_pulse_locked (imaginary, pulse));
+       }
+
+       MetricSectionSorter cmp;
+       imaginary.sort (cmp);
+
+       recompute_meters (imaginary);
+
+       return true;
+}
+
+/** places a copy of _metrics into copy and returns a pointer
+ *  to section's equivalent in copy.
+ */
+TempoSection*
+TempoMap::copy_metrics_and_point (const Metrics& metrics, Metrics& copy, TempoSection* section)
+{
+       TempoSection* ret = 0;
+
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               TempoSection* t;
+               MeterSection* m;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (t == section) {
+                               ret = new TempoSection (*t);
+                               copy.push_back (ret);
+                               continue;
+                       }
+
+                       TempoSection* cp = new TempoSection (*t);
+                       copy.push_back (cp);
+               }
+               if ((m = dynamic_cast<MeterSection *> (*i)) != 0) {
+                       MeterSection* cp = new MeterSection (*m);
+                       copy.push_back (cp);
+               }
+       }
+
+       return ret;
+}
+
+MeterSection*
+TempoMap::copy_metrics_and_point (const Metrics& metrics, Metrics& copy, MeterSection* section)
+{
+       MeterSection* ret = 0;
+
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               TempoSection* t;
+               MeterSection* m;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       TempoSection* cp = new TempoSection (*t);
+                       copy.push_back (cp);
+               }
+
+               if ((m = dynamic_cast<MeterSection *> (*i)) != 0) {
+                       if (m == section) {
+                               ret = new MeterSection (*m);
+                               copy.push_back (ret);
+                               continue;
+                       }
+                       MeterSection* cp = new MeterSection (*m);
+                       copy.push_back (cp);
+               }
+       }
+
+       return ret;
+}
+
+/** answers the question "is this a valid beat position for this tempo section?".
+ *  it returns true if the tempo section can be moved to the requested bbt position,
+ *  leaving the tempo map in a solved state.
+ * @param section the tempo section to be moved
+ * @param bbt the requested new position for the tempo section
+ * @return true if the tempo section can be moved to the position, otherwise false.
+ */
+bool
+TempoMap::can_solve_bbt (TempoSection* ts, const BBT_Time& bbt)
+{
+       Metrics copy;
+       TempoSection* tempo_copy = 0;
+
+       {
+               Glib::Threads::RWLock::ReaderLock lm (lock);
+               tempo_copy = copy_metrics_and_point (_metrics, copy, ts);
+               if (!tempo_copy) {
+                       return false;
+               }
+       }
+
+       const bool ret = solve_map_pulse (copy, tempo_copy, pulse_at_bbt_locked (copy, bbt));
+
+       Metrics::const_iterator d = copy.begin();
+       while (d != copy.end()) {
+               delete (*d);
+               ++d;
+       }
+
+       return ret;
+}
+
+/**
+* This is for a gui that needs to know the pulse or frame of a tempo section if it were to be moved to some bbt time,
+* taking any possible reordering as a consequence of this into account.
+* @param section - the section to be altered
+* @param bbt - the bbt where the altered tempo will fall
+* @return returns - the position in pulses and frames (as a pair) where the new tempo section will lie.
+*/
+pair<double, framepos_t>
+TempoMap::predict_tempo_position (TempoSection* section, const BBT_Time& bbt)
+{
+       Metrics future_map;
+       pair<double, framepos_t> ret = make_pair (0.0, 0);
+
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       TempoSection* tempo_copy = copy_metrics_and_point (_metrics, future_map, section);
+
+       const double beat = beat_at_bbt_locked (future_map, bbt);
+
+       if (solve_map_pulse (future_map, tempo_copy, pulse_at_beat_locked (future_map, beat))) {
+               ret.first = tempo_copy->pulse();
+               ret.second = tempo_copy->frame();
+       } else {
+               ret.first = section->pulse();
+               ret.second = section->frame();
+       }
+
+       Metrics::const_iterator d = future_map.begin();
+       while (d != future_map.end()) {
+               delete (*d);
+               ++d;
+       }
+       return ret;
+}
+
+void
+TempoMap::gui_move_tempo (TempoSection* ts, const framepos_t& frame, const int& sub_num)
+{
+       Metrics future_map;
+
+       if (ts->position_lock_style() == MusicTime) {
+               {
+                       /* if we're snapping to a musical grid, set the pulse exactly instead of via the supplied frame. */
+                       Glib::Threads::RWLock::WriterLock lm (lock);
+                       TempoSection* tempo_copy = copy_metrics_and_point (_metrics, future_map, ts);
+                       double beat = beat_at_frame_locked (future_map, frame);
+
+                       if (sub_num > 0) {
+                               beat = floor (beat) + (floor (((beat - floor (beat)) * (double) sub_num) + 0.5) / sub_num);
+                       } else if (sub_num == -2) {
+                               /* snap to beat */
+                               beat = floor (beat + 0.5);
+                       }
+
+                       double pulse = pulse_at_beat_locked (future_map, beat);
+
+                       if (sub_num == -3) {
+                               /* snap to  bar */
+                               pulse = floor (pulse + 0.5);
+                       }
+
+                       if (solve_map_pulse (future_map, tempo_copy, pulse)) {
+                               solve_map_pulse (_metrics, ts, pulse);
+                               recompute_meters (_metrics);
+                       }
+               }
+
+       } else {
+
+               {
+                       Glib::Threads::RWLock::WriterLock lm (lock);
+                       TempoSection* tempo_copy = copy_metrics_and_point (_metrics, future_map, ts);
+                       if (solve_map_frame (future_map, tempo_copy, frame)) {
+                               solve_map_frame (_metrics, ts, frame);
+                               recompute_meters (_metrics);
+                       }
+               }
+       }
+
+       Metrics::const_iterator d = future_map.begin();
+       while (d != future_map.end()) {
+               delete (*d);
+               ++d;
+       }
+
+       MetricPositionChanged (); // Emit Signal
+}
+
+void
+TempoMap::gui_move_meter (MeterSection* ms, const framepos_t& frame)
+{
+       Metrics future_map;
+
+       if (ms->position_lock_style() == AudioTime) {
 
-       imaginary.sort (cmp);
-       if (section->position_lock_style() == AudioTime) {
-               /* we're setting the pulse */
-               section->set_position_lock_style (MusicTime);
-               recompute_tempos (imaginary);
-               section->set_position_lock_style (AudioTime);
+               {
+                       Glib::Threads::RWLock::WriterLock lm (lock);
+                       MeterSection* copy = copy_metrics_and_point (_metrics, future_map, ms);
+
+                       if (solve_map_frame (future_map, copy, frame)) {
+                               solve_map_frame (_metrics, ms, frame);
+                               recompute_tempos (_metrics);
+                       }
+               }
        } else {
-               recompute_tempos (imaginary);
-       }
+               {
+                       Glib::Threads::RWLock::WriterLock lm (lock);
+                       MeterSection* copy = copy_metrics_and_point (_metrics, future_map, ms);
 
-       if (check_solved (imaginary, false)) {
-               recompute_meters (imaginary);
-               return true;
-       }
+                       const double beat = beat_at_frame_locked (_metrics, frame);
+                       const Timecode::BBT_Time bbt = bbt_at_beat_locked (_metrics, beat);
 
-       imaginary.sort (fcmp);
-       if (section->position_lock_style() == AudioTime) {
-               /* we're setting the pulse */
-               section->set_position_lock_style (MusicTime);
-               recompute_tempos (imaginary);
-               section->set_position_lock_style (AudioTime);
-       } else {
-               recompute_tempos (imaginary);
+                       if (solve_map_bbt (future_map, copy, bbt)) {
+                               solve_map_bbt (_metrics, ms, bbt);
+                               recompute_tempos (_metrics);
+                       }
+               }
        }
 
-       if (check_solved (imaginary, false)) {
-               recompute_meters (imaginary);
-               return true;
+       Metrics::const_iterator d = future_map.begin();
+       while (d != future_map.end()) {
+               delete (*d);
+               ++d;
        }
 
-       //dump (imaginary, std::cerr);
-
-       return false;
+       MetricPositionChanged (); // Emit Signal
 }
 
-void
-TempoMap::solve_map (Metrics& imaginary, MeterSection* section, const Meter& mt, const double& pulse)
+bool
+TempoMap::gui_change_tempo (TempoSection* ts, const Tempo& bpm)
 {
-       MeterSection* prev_ms = 0;
-       double accumulated_beats = 0.0;
-       uint32_t accumulated_bars = 0;
-
-       section->set_pulse (pulse);
+       Metrics future_map;
+       bool can_solve = false;
+       {
+               Glib::Threads::RWLock::WriterLock lm (lock);
+               TempoSection* tempo_copy = copy_metrics_and_point (_metrics, future_map, ts);
+               tempo_copy->set_beats_per_minute (bpm.beats_per_minute());
+               recompute_tempos (future_map);
 
-       for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
-               MeterSection* m;
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (prev_ms) {
-                               double const beats_in_m = (m->pulse() - prev_ms->pulse()) * prev_ms->note_divisor();
-                               accumulated_beats += beats_in_m;
-                               accumulated_bars += (beats_in_m + 1) / prev_ms->divisions_per_bar();
-                       }
-                       if (m == section){
-                               section->set_frame (frame_at_pulse_locked (imaginary, pulse));
-                               pair<double, BBT_Time> b_bbt = make_pair (accumulated_beats, BBT_Time (accumulated_bars + 1, 1, 0));
-                               section->set_beat (b_bbt);
-                               prev_ms = section;
-                               continue;
-                       }
-                       if (prev_ms) {
-                               if (m->position_lock_style() == MusicTime) {
-                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
-                                       m->set_frame (frame_at_pulse_locked (imaginary, pulse));
-                                       m->set_pulse (pulse);
-                               } else {
-                                       pair<double, BBT_Time> b_bbt = make_pair (accumulated_beats, BBT_Time (accumulated_bars + 1, 1, 0));
-                                       m->set_beat (b_bbt);
-                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
-                                       m->set_pulse (pulse);
-                               }
-                       }
-                       prev_ms = m;
+               if (check_solved (future_map)) {
+                       ts->set_beats_per_minute (bpm.beats_per_minute());
+                       recompute_map (_metrics);
+                       can_solve = true;
                }
        }
 
-       if (section->position_lock_style() == AudioTime) {
-               /* we're setting the pulse */
-               section->set_position_lock_style (MusicTime);
-               recompute_meters (imaginary);
-               section->set_position_lock_style (AudioTime);
-       } else {
-               recompute_meters (imaginary);
+       Metrics::const_iterator d = future_map.begin();
+       while (d != future_map.end()) {
+               delete (*d);
+               ++d;
        }
+       if (can_solve) {
+               MetricPositionChanged (); // Emit Signal
+       }
+       return can_solve;
 }
 
 void
-TempoMap::solve_map (Metrics& imaginary, MeterSection* section, const Meter& mt, const framepos_t& frame)
-{
-       MeterSection* prev_ms = 0;
+TempoMap::gui_dilate_tempo (TempoSection* ts, const framepos_t& frame, const framepos_t& end_frame, const double& pulse)
+{
+       /*
+         Ts (future prev_t)   Tnext
+         |                    |
+         |     [drag^]        |
+         |----------|----------
+               e_f  pulse(frame)
+       */
 
-       if (!section->movable()) {
-               TempoSection* first_t;
-               for (Metrics::const_iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
-                       TempoSection* t;
+       Metrics future_map;
+
+       {
+               Glib::Threads::RWLock::WriterLock lm (lock);
+
+               if (!ts) {
+                       return;
+               }
+
+               TempoSection* prev_t = copy_metrics_and_point (_metrics, future_map, ts);
+               TempoSection* prev_to_prev_t = 0;
+               const frameoffset_t fr_off = end_frame - frame;
+
+               if (prev_t && prev_t->pulse() > 0.0) {
+                       prev_to_prev_t = const_cast<TempoSection*>(&tempo_section_at_frame_locked (future_map, prev_t->frame() - 1));
+               }
+
+               TempoSection* next_t = 0;
+               for (Metrics::iterator i = future_map.begin(); i != future_map.end(); ++i) {
+                       TempoSection* t = 0;
                        if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
-                               if (!t->movable()) {
-                                       t->set_active (true);
-                                       first_t = t;
-                               }
-                               if (t->movable() && t->active () && t->position_lock_style() == AudioTime && t->frame() < frame) {
-                                       t->set_active (false);
-                                       t->set_pulse (0.0);
-                               } else if (t->movable() && t->position_lock_style() == AudioTime && t->frame() > frame) {
-                                       t->set_active (true);
-                               } else if (t->movable() && t->position_lock_style() == AudioTime && t->frame() == frame) {
-                                       return;
+                               if (t->frame() > ts->frame()) {
+                                       next_t = t;
+                                       break;
                                }
                        }
                }
+               /* minimum allowed measurement distance in frames */
+               const framepos_t min_dframe = 2;
 
-               Metrics future_map;
-               TempoSection* new_section = copy_metrics_and_point (future_map, first_t);
-
-               new_section->set_frame (frame);
-               new_section->set_pulse (0.0);
-               new_section->set_active (true);
+               /* the change in frames is the result of changing the slope of at most 2 previous tempo sections.
+                  constant to constant is straightforward, as the tempo prev to prev_t has constant slope.
+               */
+               double contribution = 0.0;
 
-               if (solve_map (future_map, new_section, Tempo (new_section->beats_per_minute(), new_section->note_type()), frame)) {
-                       first_t->set_frame (frame);
-                       first_t->set_pulse (0.0);
-                       first_t->set_active (true);
-                       solve_map (imaginary, first_t, Tempo (first_t->beats_per_minute(), first_t->note_type()), frame);
-               } else {
-                       return;
+               if (next_t && prev_to_prev_t && prev_to_prev_t->type() == TempoSection::Ramp) {
+                       contribution = (prev_t->frame() - prev_to_prev_t->frame()) / (double) (next_t->frame() - prev_to_prev_t->frame());
                }
-       }
 
-       double accumulated_beats = 0.0;
-       uint32_t accumulated_bars = 0;
+               const frameoffset_t prev_t_frame_contribution = fr_off - (contribution * (double) fr_off);
 
-       section->set_frame (frame);
+               const double start_pulse = prev_t->pulse_at_frame (frame, _frame_rate);
+               const double end_pulse = prev_t->pulse_at_frame (end_frame, _frame_rate);
 
-       for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
-               MeterSection* m;
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (prev_ms) {
-                               const double beats_in_m = (m->pulse() - prev_ms->pulse()) * prev_ms->note_divisor();
-                               accumulated_beats += beats_in_m;
-                               accumulated_bars += (beats_in_m + 1) / prev_ms->divisions_per_bar();
-                       }
-                       if (m == section){
-                               /*
-                                 here we define the pulse for this frame.
-                                 we're going to set it 'incorrectly' to the next integer and use this 'error'
-                                 as an offset to the map as far as users of the public methods are concerned.
-                                 (meters should go on absolute pulses to keep us sane)
-                               */
-                               pair<double, BBT_Time> b_bbt = make_pair (accumulated_beats, BBT_Time (accumulated_bars + 1, 1, 0));
-                               if (m->movable()) {
-                                       m->set_pulse (pulse_at_frame_locked (imaginary, frame));
+               double new_bpm;
+
+               if (prev_t->type() == TempoSection::Constant || prev_t->c_func() == 0.0) {
+
+                       if (prev_t->position_lock_style() == MusicTime) {
+                               if (prev_to_prev_t && prev_to_prev_t->type() == TempoSection::Ramp) {
+                                       if (frame > prev_to_prev_t->frame() + min_dframe && (frame + prev_t_frame_contribution) > prev_to_prev_t->frame() + min_dframe) {
+
+                                               new_bpm = prev_t->beats_per_minute() * ((frame - prev_to_prev_t->frame())
+                                                                                       / (double) ((frame + prev_t_frame_contribution) - prev_to_prev_t->frame()));
+                                       } else {
+                                               new_bpm = prev_t->beats_per_minute();
+                                       }
                                } else {
-                                       m->set_pulse (0.0);
+                                       /* prev to prev is irrelevant */
+
+                                       if (start_pulse > prev_t->pulse() && end_pulse > prev_t->pulse()) {
+                                               new_bpm = prev_t->beats_per_minute() * ((start_pulse - prev_t->pulse()) / (end_pulse - prev_t->pulse()));
+                                       } else {
+                                               new_bpm = prev_t->beats_per_minute();
+                                       }
                                }
-                               m->set_beat (b_bbt);
-                               prev_ms = m;
-                               continue;
-                       }
-                       if (prev_ms) {
-                               if (m->position_lock_style() == MusicTime) {
-                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
-                                       m->set_frame (frame_at_pulse_locked (imaginary, pulse));
-                                       m->set_pulse (pulse);
+                       } else {
+                               /* AudioTime */
+                               if (prev_to_prev_t && prev_to_prev_t->type() == TempoSection::Ramp) {
+                                       if (frame > prev_to_prev_t->frame() + min_dframe && end_frame > prev_to_prev_t->frame() + min_dframe) {
+
+                                               new_bpm = prev_t->beats_per_minute() * ((frame - prev_to_prev_t->frame())
+                                                                                       / (double) ((end_frame) - prev_to_prev_t->frame()));
+                                       } else {
+                                               new_bpm = prev_t->beats_per_minute();
+                                       }
                                } else {
-                                       pair<double, BBT_Time> b_bbt = make_pair (accumulated_beats, BBT_Time (accumulated_bars + 1, 1, 0));
-                                       m->set_beat (b_bbt);
-                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
-                                       m->set_pulse (pulse);
+                                       /* prev_to_prev_t is irrelevant */
+
+                                       if (frame > prev_t->frame() + min_dframe && end_frame > prev_t->frame() + min_dframe) {
+                                               new_bpm = prev_t->beats_per_minute() * ((frame - prev_t->frame()) / (double) (end_frame - prev_t->frame()));
+                                       } else {
+                                               new_bpm = prev_t->beats_per_minute();
+                                       }
+                               }
+                       }
+               } else {
+
+                       double frame_ratio = 1.0;
+                       double pulse_ratio = 1.0;
+                       const framepos_t pulse_pos = prev_t->frame_at_pulse (pulse, _frame_rate);
+
+                       if (prev_to_prev_t) {
+                               if (pulse_pos > prev_to_prev_t->frame() + min_dframe && (pulse_pos - fr_off) > prev_to_prev_t->frame() + min_dframe) {
+                                       frame_ratio = (((pulse_pos - fr_off) - prev_to_prev_t->frame()) / (double) ((pulse_pos) - prev_to_prev_t->frame()));
+                               }
+                               if (end_pulse > prev_to_prev_t->pulse() && start_pulse > prev_to_prev_t->pulse()) {
+                                       pulse_ratio = ((start_pulse - prev_to_prev_t->pulse()) / (end_pulse - prev_to_prev_t->pulse()));
+                               }
+                       } else {
+                               if (pulse_pos > prev_t->frame() + min_dframe && (pulse_pos - fr_off) > prev_t->frame() + min_dframe) {
+                                       frame_ratio = (((pulse_pos - fr_off) - prev_t->frame()) / (double) ((pulse_pos) - prev_t->frame()));
                                }
+                               pulse_ratio = (start_pulse / end_pulse);
                        }
-                       prev_ms = m;
+                       new_bpm = prev_t->beats_per_minute() * (pulse_ratio * frame_ratio);
+               }
+
+               /* don't clamp and proceed here.
+                  testing has revealed that this can go negative,
+                  which is an entirely different thing to just being too low.
+               */
+               if (new_bpm < 0.5) {
+                       return;
+               }
+               new_bpm = min (new_bpm, (double) 1000.0);
+               prev_t->set_beats_per_minute (new_bpm);
+               recompute_tempos (future_map);
+               recompute_meters (future_map);
+
+               if (check_solved (future_map)) {
+                       ts->set_beats_per_minute (new_bpm);
+                       recompute_tempos (_metrics);
+                       recompute_meters (_metrics);
                }
        }
 
-       if (section->position_lock_style() == MusicTime) {
-               /* we're setting the frame */
-               section->set_position_lock_style (AudioTime);
-               recompute_meters (imaginary);
-               section->set_position_lock_style (MusicTime);
-       } else {
-               recompute_meters (imaginary);
+       Metrics::const_iterator d = future_map.begin();
+       while (d != future_map.end()) {
+               delete (*d);
+               ++d;
        }
-       //dump (imaginary, std::cerr);
+
+       MetricPositionChanged (); // Emit Signal
 }
 
 framecnt_t
@@ -2335,13 +2801,11 @@ TempoMap::bbt_duration_at (framepos_t pos, const BBT_Time& bbt, int dir)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
 
-       double const tick_at_time = beat_at_frame_locked (_metrics, pos) * BBT_Time::ticks_per_beat;
-       double const bbt_ticks = bbt.ticks + (bbt.beats * BBT_Time::ticks_per_beat);
-       double const total_beats = (tick_at_time + bbt_ticks) / BBT_Time::ticks_per_beat;
-       framecnt_t const time_at_bbt = frame_at_beat_locked (_metrics, total_beats);
-       framecnt_t const ret = time_at_bbt;
+       const double tick_at_time = beat_at_frame_locked (_metrics, pos) * BBT_Time::ticks_per_beat;
+       const double bbt_ticks = bbt.ticks + (bbt.beats * BBT_Time::ticks_per_beat);
+       const double total_beats = (tick_at_time + bbt_ticks) / BBT_Time::ticks_per_beat;
 
-       return ret;
+       return frame_at_beat_locked (_metrics, total_beats);
 }
 
 framepos_t
@@ -2447,69 +2911,18 @@ TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, RoundMode dir)
                }
        }
 
-       framepos_t const ret_frame = frame_at_beat_locked (_metrics, beats + (ticks / BBT_Time::ticks_per_beat));
+       const framepos_t ret_frame = frame_at_beat_locked (_metrics, beats + (ticks / BBT_Time::ticks_per_beat));
 
        return ret_frame;
 }
 
-void
-TempoMap::round_bbt (BBT_Time& when, const int32_t& sub_num)
-{
-       if (sub_num == -1) {
-               const double bpb = meter_section_at (bbt_to_beats_locked (_metrics, when)).divisions_per_bar();
-               if ((double) when.beats > bpb / 2.0) {
-                       ++when.bars;
-               }
-               when.beats = 1;
-               when.ticks = 0;
-               return;
-       } else if (sub_num == 0) {
-               const double bpb = meter_section_at (bbt_to_beats_locked (_metrics, when)).divisions_per_bar();
-               if ((double) when.ticks > BBT_Time::ticks_per_beat / 2.0) {
-                       ++when.beats;
-                       while ((double) when.beats > bpb) {
-                               ++when.bars;
-                               when.beats -= (uint32_t) floor (bpb);
-                       }
-               }
-               when.ticks = 0;
-               return;
-       }
-       const uint32_t ticks_one_subdivisions_worth = BBT_Time::ticks_per_beat / sub_num;
-       double rem;
-       if ((rem = fmod ((double) when.ticks, (double) ticks_one_subdivisions_worth)) > (ticks_one_subdivisions_worth / 2.0)) {
-               /* closer to the next subdivision, so shift forward */
-
-               when.ticks = when.ticks + (ticks_one_subdivisions_worth - rem);
-
-               if (when.ticks > Timecode::BBT_Time::ticks_per_beat) {
-                       ++when.beats;
-                       when.ticks -= Timecode::BBT_Time::ticks_per_beat;
-               }
-
-       } else if (rem > 0) {
-               /* closer to previous subdivision, so shift backward */
-
-               if (rem > when.ticks) {
-                       if (when.beats == 0) {
-                               /* can't go backwards past zero, so ... */
-                       }
-                       /* step back to previous beat */
-                       --when.beats;
-                       when.ticks = Timecode::BBT_Time::ticks_per_beat - rem;
-               } else {
-                       when.ticks = when.ticks - rem;
-               }
-       }
-}
-
 framepos_t
 TempoMap::round_to_type (framepos_t frame, RoundMode dir, BBTPointType type)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
 
-       double const beat_at_framepos = beat_at_frame_locked (_metrics, frame);
-       BBT_Time bbt (beats_to_bbt_locked (_metrics, beat_at_framepos));
+       const double beat_at_framepos = beat_at_frame_locked (_metrics, frame);
+       BBT_Time bbt (bbt_at_beat_locked (_metrics, beat_at_framepos));
 
        switch (type) {
        case Bar:
@@ -2517,22 +2930,22 @@ TempoMap::round_to_type (framepos_t frame, RoundMode dir, BBTPointType type)
                        /* find bar previous to 'frame' */
                        bbt.beats = 1;
                        bbt.ticks = 0;
-                       return frame_time (bbt);
+                       return frame_at_bbt_locked (_metrics, bbt);
 
                } else if (dir > 0) {
                        /* find bar following 'frame' */
                        ++bbt.bars;
                        bbt.beats = 1;
                        bbt.ticks = 0;
-                       return frame_time (bbt);
+                       return frame_at_bbt_locked (_metrics, bbt);
                } else {
                        /* true rounding: find nearest bar */
-                       framepos_t raw_ft = frame_time (bbt);
+                       framepos_t raw_ft = frame_at_bbt_locked (_metrics, bbt);
                        bbt.beats = 1;
                        bbt.ticks = 0;
-                       framepos_t prev_ft = frame_time (bbt);
+                       framepos_t prev_ft = frame_at_bbt_locked (_metrics, bbt);
                        ++bbt.bars;
-                       framepos_t next_ft = frame_time (bbt);
+                       framepos_t next_ft = frame_at_bbt_locked (_metrics, bbt);
 
                        if ((raw_ft - prev_ft) > (next_ft - prev_ft) / 2) { 
                                return next_ft;
@@ -2562,44 +2975,48 @@ TempoMap::get_grid (vector<TempoMap::BBTPoint>& points,
                    framepos_t lower, framepos_t upper)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       int32_t const upper_beat = (int32_t) ceil (beat_at_frame_locked (_metrics, upper));
-       int32_t cnt = floor (beat_at_frame_locked (_metrics, lower));
+       int32_t cnt = ceil (beat_at_frame_locked (_metrics, lower));
+       framecnt_t pos = 0;
        /* although the map handles negative beats, bbt doesn't. */
        if (cnt < 0.0) {
                cnt = 0.0;
        }
-       while (cnt <= upper_beat) {
-               framecnt_t pos = frame_at_beat_locked (_metrics, cnt);
-               TempoSection const tempo = tempo_section_at_locked (pos);
-               MeterSection const meter = meter_section_at_locked (pos);
-               BBT_Time const bbt = beats_to_bbt (cnt);
 
-               points.push_back (BBTPoint (meter, tempo_at_locked (pos), pos, bbt.bars, bbt.beats, tempo.get_c_func()));
+       if (frame_at_beat_locked (_metrics, cnt) >= upper) {
+               return;
+       }
+
+       while (pos < upper) {
+               pos = frame_at_beat_locked (_metrics, cnt);
+               const TempoSection tempo = tempo_section_at_frame_locked (_metrics, pos);
+               const MeterSection meter = meter_section_at_frame_locked (_metrics, pos);
+               const BBT_Time bbt = bbt_at_beat_locked (_metrics, cnt);
+               points.push_back (BBTPoint (meter, tempo_at_frame_locked (_metrics, pos), pos, bbt.bars, bbt.beats, tempo.c_func()));
                ++cnt;
        }
 }
 
 const TempoSection&
-TempoMap::tempo_section_at (framepos_t frame) const
+TempoMap::tempo_section_at_frame (framepos_t frame) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       return tempo_section_at_locked (frame);
+       return tempo_section_at_frame_locked (_metrics, frame);
 }
 
 const TempoSection&
-TempoMap::tempo_section_at_locked (framepos_t frame) const
+TempoMap::tempo_section_at_frame_locked (const Metrics& metrics, framepos_t frame) const
 {
        Metrics::const_iterator i;
        TempoSection* prev = 0;
 
-       for (i = _metrics.begin(); i != _metrics.end(); ++i) {
+       for (i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
 
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
                        if (!t->active()) {
                                continue;
                        }
-                       if (t->frame() > frame) {
+                       if (prev && t->frame() > frame) {
                                break;
                        }
 
@@ -2615,6 +3032,24 @@ TempoMap::tempo_section_at_locked (framepos_t frame) const
        return *prev;
 }
 
+const TempoSection&
+TempoMap::tempo_section_at_beat_locked (const Metrics& metrics, const double& beat) const
+{
+       TempoSection* prev_t = 0;
+       const MeterSection* prev_m = &meter_section_at_beat_locked (metrics, beat);
+
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               TempoSection* t;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (prev_t && ((t->pulse() - prev_m->pulse()) * prev_m->note_divisor()) + prev_m->beat() > beat) {
+                               break;
+                       }
+                       prev_t = t;
+               }
+
+       }
+       return *prev_t;
+}
 
 /* don't use this to calculate length (the tempo is only correct for this frame).
    do that stuff based on the beat_at_frame and frame_at_beat api
@@ -2624,7 +3059,7 @@ TempoMap::frames_per_beat_at (const framepos_t& frame, const framecnt_t& sr) con
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
 
-       const TempoSection* ts_at = &tempo_section_at_locked (frame);
+       const TempoSection* ts_at = &tempo_section_at_frame_locked (_metrics, frame);
        const TempoSection* ts_after = 0;
        Metrics::const_iterator i;
 
@@ -2643,107 +3078,139 @@ TempoMap::frames_per_beat_at (const framepos_t& frame, const framecnt_t& sr) con
        }
 
        if (ts_after) {
-               return  (60.0 * _frame_rate) / (ts_at->tempo_at_frame (frame, _frame_rate));
+               return  (60.0 * _frame_rate) / (ts_at->tempo_at_frame (frame, _frame_rate) * ts_at->note_type());
        }
        /* must be treated as constant tempo */
        return ts_at->frames_per_beat (_frame_rate);
 }
 
-const Tempo
-TempoMap::tempo_at (const framepos_t& frame) const
+const MeterSection&
+TempoMap::meter_section_at_frame_locked (const Metrics& metrics, framepos_t frame) const
 {
-       Glib::Threads::RWLock::ReaderLock lm (lock);
-       return tempo_at_locked (frame);
-}
+       Metrics::const_iterator i;
+       MeterSection* prev = 0;
 
-const Tempo
-TempoMap::tempo_at_locked (const framepos_t& frame) const
-{
-       TempoSection* prev_ts = 0;
+       for (i = metrics.begin(); i != metrics.end(); ++i) {
+               MeterSection* m;
 
-       Metrics::const_iterator i;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
 
-       for (i = _metrics.begin(); i != _metrics.end(); ++i) {
-               TempoSection* t;
-               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
-                       if (!t->active()) {
-                               continue;
-                       }
-                       if ((prev_ts) && t->frame() > frame) {
-                               /* t is the section past frame */
-                               double const ret = prev_ts->tempo_at_frame (frame, _frame_rate) * prev_ts->note_type();
-                               Tempo const ret_tempo (ret, prev_ts->note_type());
-                               return ret_tempo;
+                       if (prev && (*i)->frame() > frame) {
+                               break;
                        }
-                       prev_ts = t;
+
+                       prev = m;
                }
        }
 
-       double const ret = prev_ts->beats_per_minute();
-       Tempo const ret_tempo (ret, prev_ts->note_type ());
+       if (prev == 0) {
+               fatal << endmsg;
+               abort(); /*NOTREACHED*/
+       }
 
-       return ret_tempo;
+       return *prev;
 }
 
+
 const MeterSection&
-TempoMap::meter_section_at (framepos_t frame) const
+TempoMap::meter_section_at_frame (framepos_t frame) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       return meter_section_at_locked (frame);
+       return meter_section_at_frame_locked (_metrics, frame);
 }
 
 const MeterSection&
-TempoMap::meter_section_at_locked (framepos_t frame) const
+TempoMap::meter_section_at_beat_locked (const Metrics& metrics, const double& beat) const
 {
-       //framepos_t const frame_off = frame + frame_offset_at (_metrics, frame);
-       Metrics::const_iterator i;
-       MeterSection* prev = 0;
+       MeterSection* prev_m = 0;
 
-       for (i = _metrics.begin(); i != _metrics.end(); ++i) {
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                MeterSection* m;
-
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-
-                       if (prev && (*i)->frame() > frame) {
+                       if (prev_m && m->beat() > beat) {
                                break;
                        }
-
-                       prev = m;
+                       prev_m = m;
                }
-       }
 
-       if (prev == 0) {
-               fatal << endmsg;
-               abort(); /*NOTREACHED*/
        }
+       return *prev_m;
+}
 
-       return *prev;
+const MeterSection&
+TempoMap::meter_section_at_beat (double beat) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return meter_section_at_beat_locked (_metrics, beat);
 }
 
 const Meter&
-TempoMap::meter_at (framepos_t frame) const
+TempoMap::meter_at_frame (framepos_t frame) const
 {
        TempoMetric m (metric_at (frame));
        return m.meter();
 }
 
-const MeterSection&
-TempoMap::meter_section_at (const double& beat) const
+void
+TempoMap::fix_legacy_session ()
 {
-       MeterSection* prev_ms = 0;
-       Glib::Threads::RWLock::ReaderLock lm (lock);
+       MeterSection* prev_m = 0;
+       TempoSection* prev_t = 0;
 
-       for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+       for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
                MeterSection* m;
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (prev_ms && m->beat() > beat) {
-                               break;
+               TempoSection* t;
+
+               if ((m = dynamic_cast<MeterSection*>(*i)) != 0) {
+                       if (!m->movable()) {
+                               pair<double, BBT_Time> bbt = make_pair (0.0, BBT_Time (1, 1, 0));
+                               m->set_beat (bbt);
+                               m->set_pulse (0.0);
+                               m->set_frame (0);
+                               m->set_position_lock_style (AudioTime);
+                               prev_m = m;
+                               continue;
+                       }
+                       if (prev_m) {
+                               pair<double, BBT_Time> start = make_pair (((m->bbt().bars - 1) * prev_m->note_divisor())
+                                                                         + (m->bbt().beats - 1)
+                                                                         + (m->bbt().ticks / BBT_Time::ticks_per_beat)
+                                                                         , m->bbt());
+                               m->set_beat (start);
+                               const double start_beat = ((m->bbt().bars - 1) * prev_m->note_divisor())
+                                       + (m->bbt().beats - 1)
+                                       + (m->bbt().ticks / BBT_Time::ticks_per_beat);
+                               m->set_pulse (start_beat / prev_m->note_divisor());
+                       }
+                       prev_m = m;
+               } else if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
+
+                       if (!t->active()) {
+                               continue;
                        }
-                       prev_ms = m;
-               }
 
+                       if (!t->movable()) {
+                               t->set_pulse (0.0);
+                               t->set_frame (0);
+                               t->set_position_lock_style (AudioTime);
+                               prev_t = t;
+                               continue;
+                       }
+
+                       if (prev_t) {
+                               const double beat = ((t->legacy_bbt().bars - 1) * ((prev_m) ? prev_m->note_divisor() : 4.0))
+                                       + (t->legacy_bbt().beats - 1)
+                                       + (t->legacy_bbt().ticks / BBT_Time::ticks_per_beat);
+                               if (prev_m) {
+                                       t->set_pulse (beat / prev_m->note_divisor());
+                               } else {
+                                       /* really shouldn't happen but.. */
+                                       t->set_pulse (beat / 4.0);
+                               }
+                       }
+                       prev_t = t;
+               }
        }
-       return *prev_ms;
 }
 
 XMLNode&
@@ -2810,32 +3277,19 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
                        MetricSectionSorter cmp;
                        _metrics.sort (cmp);
                }
+
                /* check for legacy sessions where bbt was the base musical unit for tempo */
-               for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
-                       MeterSection* m;
+               for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
                        TempoSection* t;
-                       MeterSection* prev_ms = 0;
-                       TempoSection* prev_ts = 0;
-                       if ((m = dynamic_cast<MeterSection*>(*i)) != 0) {
-                               if (prev_ms && prev_ms->pulse() < 0.0) {
-                                       /*XX we cannot possibly make this work??. */
-                                       pair<double, BBT_Time> start = make_pair (((prev_ms->bbt().bars - 1) * prev_ms->note_divisor()) + (prev_ms->bbt().beats - 1) + (prev_ms->bbt().ticks / BBT_Time::ticks_per_beat), prev_ms->bbt());
-                                       prev_ms->set_beat (start);
-                                       const double start_pulse = ((prev_ms->bbt().bars - 1) * prev_ms->note_divisor()) + (prev_ms->bbt().beats - 1) + (prev_ms->bbt().ticks / BBT_Time::ticks_per_beat);
-                                       prev_ms->set_pulse (start_pulse);
-                               }
-                               prev_ms = m;
-                       } else if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
-                               if (!t->active()) {
-                                       continue;
-                               }
-                               if (prev_ts && prev_ts->pulse() < 0.0) {
-                                       double const start = ((prev_ts->legacy_bbt().bars - 1) * prev_ms->note_divisor()) + (prev_ts->legacy_bbt().beats - 1) + (prev_ts->legacy_bbt().ticks / BBT_Time::ticks_per_beat);
-                                       prev_ts->set_pulse (start);
+                       if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                               if (t->legacy_bbt().bars != 0) {
+                                       fix_legacy_session();
+                                       break;
                                }
-                               prev_ts = t;
+                               break;
                        }
                }
+
                /* check for multiple tempo/meters at the same location, which
                   ardour2 somehow allowed.
                */
@@ -2844,19 +3298,19 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
                for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
                        if (prev != _metrics.end()) {
                                MeterSection* ms;
-                               MeterSection* prev_ms;
+                               MeterSection* prev_m;
                                TempoSection* ts;
-                               TempoSection* prev_ts;
-                               if ((prev_ms = dynamic_cast<MeterSection*>(*prev)) != 0 && (ms = dynamic_cast<MeterSection*>(*i)) != 0) {
-                                       if (prev_ms->pulse() == ms->pulse()) {
-                                               cerr << string_compose (_("Multiple meter definitions found at %1"), prev_ms->pulse()) << endmsg;
-                                               error << string_compose (_("Multiple meter definitions found at %1"), prev_ms->pulse()) << endmsg;
+                               TempoSection* prev_t;
+                               if ((prev_m = dynamic_cast<MeterSection*>(*prev)) != 0 && (ms = dynamic_cast<MeterSection*>(*i)) != 0) {
+                                       if (prev_m->pulse() == ms->pulse()) {
+                                               cerr << string_compose (_("Multiple meter definitions found at %1"), prev_m->pulse()) << endmsg;
+                                               error << string_compose (_("Multiple meter definitions found at %1"), prev_m->pulse()) << endmsg;
                                                return -1;
                                        }
-                               } else if ((prev_ts = dynamic_cast<TempoSection*>(*prev)) != 0 && (ts = dynamic_cast<TempoSection*>(*i)) != 0) {
-                                       if (prev_ts->pulse() == ts->pulse()) {
-                                               cerr << string_compose (_("Multiple tempo definitions found at %1"), prev_ts->pulse()) << endmsg;
-                                               error << string_compose (_("Multiple tempo definitions found at %1"), prev_ts->pulse()) << endmsg;
+                               } else if ((prev_t = dynamic_cast<TempoSection*>(*prev)) != 0 && (ts = dynamic_cast<TempoSection*>(*i)) != 0) {
+                                       if (prev_t->pulse() == ts->pulse()) {
+                                               cerr << string_compose (_("Multiple tempo definitions found at %1"), prev_t->pulse()) << endmsg;
+                                               error << string_compose (_("Multiple tempo definitions found at %1"), prev_t->pulse()) << endmsg;
                                                return -1;
                                        }
                                }
@@ -2878,7 +3332,7 @@ TempoMap::dump (const Metrics& metrics, std::ostream& o) const
        Glib::Threads::RWLock::ReaderLock lm (lock, Glib::Threads::TRY_LOCK);
        const MeterSection* m;
        const TempoSection* t;
-       const TempoSection* prev_ts = 0;
+       const TempoSection* prev_t = 0;
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
 
@@ -2886,11 +3340,11 @@ TempoMap::dump (const Metrics& metrics, std::ostream& o) const
                        o << "Tempo @ " << *i << t->beats_per_minute() << " BPM (pulse = 1/" << t->note_type() << ") at " << t->pulse() << " frame= " << t->frame() << " (movable? "
                          << t->movable() << ')' << " pos lock: " << enum_2_string (t->position_lock_style()) << std::endl;
                        o << "current      : " << t->beats_per_minute() << " | " << t->pulse() << " | " << t->frame() << std::endl;
-                       if (prev_ts) {
-                               o << "previous     : " << prev_ts->beats_per_minute() << " | " << prev_ts->pulse() << " | " << prev_ts->frame() << std::endl;
-                               o << "calculated   : " << prev_ts->tempo_at_pulse (t->pulse()) *  prev_ts->note_type() << " | " << prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate) <<  " | " << prev_ts->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate) << std::endl;
+                       if (prev_t) {
+                               o << "previous     : " << prev_t->beats_per_minute() << " | " << prev_t->pulse() << " | " << prev_t->frame() << std::endl;
+                               o << "calculated   : " << prev_t->tempo_at_pulse (t->pulse()) *  prev_t->note_type() << " | " << prev_t->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate) <<  " | " << prev_t->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate) << std::endl;
                        }
-                       prev_ts = t;
+                       prev_t = t;
                } else if ((m = dynamic_cast<const MeterSection*>(*i)) != 0) {
                        o << "Meter @ " << *i << ' ' << m->divisions_per_bar() << '/' << m->note_divisor() << " at " << m->bbt() << " frame= " << m->frame()
                          << " pulse: " << m->pulse() <<  " beat : " << m->beat() << " pos lock: " << enum_2_string (m->position_lock_style()) << " (movable? " << m->movable() << ')' << endl;
@@ -2993,7 +3447,7 @@ TempoMap::insert_time (framepos_t where, framecnt_t amount)
                                                        continue;
                                                }
                                                const double beat = beat_at_pulse_locked (_metrics, t->pulse());
-                                               pair<double, BBT_Time> start = make_pair (beat, beats_to_bbt_locked (_metrics, beat));
+                                               pair<double, BBT_Time> start = make_pair (beat, bbt_at_beat_locked (_metrics, beat));
                                                ms->set_beat (start);
                                                ms->set_pulse (t->pulse());
                                        }
@@ -3015,7 +3469,7 @@ TempoMap::insert_time (framepos_t where, framecnt_t amount)
                                tempo = t;
                                // cerr << "NEW TEMPO, frame = " << (*i)->frame() << " beat = " << (*i)->pulse() <<endl;
                        } else if ((m = dynamic_cast<MeterSection*>(*i)) != 0) {
-                               bbt_time (m->frame(), bbt);
+                               bbt = bbt_at_frame_locked (_metrics, m->frame());
 
                                // cerr << "timestamp @ " << (*i)->frame() << " with " << bbt.bars << "|" << bbt.beats << "|" << bbt.ticks << " => ";
 
@@ -3122,14 +3576,18 @@ TempoMap::remove_time (framepos_t where, framecnt_t amount)
 framepos_t
 TempoMap::framepos_plus_beats (framepos_t pos, Evoral::Beats beats) const
 {
-       return frame_at_beat (beat_at_frame (pos) + beats.to_double());
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       return frame_at_beat_locked (_metrics, beat_at_frame_locked (_metrics, pos) + beats.to_double());
 }
 
 /** Subtract some (fractional) beats from a frame position, and return the result in frames */
 framepos_t
 TempoMap::framepos_minus_beats (framepos_t pos, Evoral::Beats beats) const
 {
-       return frame_at_beat (beat_at_frame (pos) - beats.to_double());
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       return frame_at_beat_locked (_metrics, beat_at_frame_locked (_metrics, pos) - beats.to_double());
 }
 
 /** Add the BBT interval op to pos and return the result */
@@ -3138,7 +3596,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
 
-       BBT_Time pos_bbt = beats_to_bbt_locked (_metrics, beat_at_frame_locked (_metrics, pos));
+       BBT_Time pos_bbt = bbt_at_beat_locked (_metrics, beat_at_frame_locked (_metrics, pos));
        pos_bbt.ticks += op.ticks;
        if (pos_bbt.ticks >= BBT_Time::ticks_per_beat) {
                ++pos_bbt.beats;
@@ -3146,15 +3604,15 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op) const
        }
        pos_bbt.beats += op.beats;
        /* the meter in effect will start on the bar */
-       double divisions_per_bar = meter_section_at (bbt_to_beats_locked (_metrics, BBT_Time (pos_bbt.bars + op.bars, 1, 0))).divisions_per_bar();
+       double divisions_per_bar = meter_section_at_beat (beat_at_bbt_locked (_metrics, BBT_Time (pos_bbt.bars + op.bars, 1, 0))).divisions_per_bar();
        while (pos_bbt.beats >= divisions_per_bar + 1) {
                ++pos_bbt.bars;
-               divisions_per_bar = meter_section_at (bbt_to_beats_locked (_metrics, BBT_Time (pos_bbt.bars + op.bars, 1, 0))).divisions_per_bar();
+               divisions_per_bar = meter_section_at_beat (beat_at_bbt_locked (_metrics, BBT_Time (pos_bbt.bars + op.bars, 1, 0))).divisions_per_bar();
                pos_bbt.beats -= divisions_per_bar;
        }
        pos_bbt.bars += op.bars;
 
-       return frame_time_locked (_metrics, pos_bbt);
+       return frame_at_bbt_locked (_metrics, pos_bbt);
 }
 
 /** Count the number of beats that are equivalent to distance when going forward,
@@ -3163,7 +3621,9 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op) const
 Evoral::Beats
 TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 {
-       return Evoral::Beats (beat_at_frame (pos + distance) - beat_at_frame (pos));
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       return Evoral::Beats (beat_at_frame_locked (_metrics, pos + distance) - beat_at_frame_locked (_metrics, pos));
 }
 
 struct bbtcmp {