b = manage (new Button (_("Invert")));
Gtkmm2ext::UI::instance()->set_tip (*b, _("Click to invert current selected playback channels"));
playback_controls->pack_start (*b);
playback_mask_controls.push_back (b);
b->signal_clicked().connect (sigc::mem_fun (*this, &MidiChannelSelectorWindow::invert_playback_mask));
b = manage (new Button (_("Invert")));
Gtkmm2ext::UI::instance()->set_tip (*b, _("Click to invert current selected playback channels"));
playback_controls->pack_start (*b);
playback_mask_controls.push_back (b);
b->signal_clicked().connect (sigc::mem_fun (*this, &MidiChannelSelectorWindow::invert_playback_mask));