boost::shared_ptr<MidiSource> src = region->midi_source(0);
src->load_model();
boost::shared_ptr<MidiModel> old_model = src->model();
boost::shared_ptr<MidiSource> new_src = boost::dynamic_pointer_cast<MidiSource>(nsrcs[0]);
boost::shared_ptr<MidiSource> src = region->midi_source(0);
src->load_model();
boost::shared_ptr<MidiModel> old_model = src->model();
boost::shared_ptr<MidiSource> new_src = boost::dynamic_pointer_cast<MidiSource>(nsrcs[0]);