+ int tracks_ = audio_staffs_.size ();
+
+ midi_stream.write (Midi_header (1, tracks_, 384));
+ debug_output (_ ("Track...") + " ", false);
+
+ //Find the first Audio_item in the performance, so all staves start
+ //at the same tick.
+ Moment start_mom = 0;
+ for (vsize i = 0; i < audio_elements_.size (); i++)
+ if (Audio_item *item = dynamic_cast<Audio_item *>(audio_elements_[i]))
+ start_mom = min (start_mom, item->audio_column_->when ());
+
+ for (vsize i = 0; i < audio_staffs_.size (); i++)
+ {
+ Audio_staff *s = audio_staffs_[i];
+ if (Audio_control_track_staff *c =
+ dynamic_cast<Audio_control_track_staff *>(s))
+ {
+ // The control track, created by Control_track_performer, should
+ // contain a placeholder for the name of the MIDI sequence as its
+ // initial audio element. Fill in the name of the sequence to
+ // this element before outputting MIDI.
+ assert (!c->audio_items_.empty ());
+ Audio_text *text =
+ dynamic_cast<Audio_text *>(c->audio_items_.front ());
+ assert (text != 0);
+ assert (text->type_ == Audio_text::TRACK_NAME);
+ assert (text->text_string_ == "control track");
+ text->text_string_ = performance_name;
+ }
+ debug_output ("[" + ::to_string (i), true);
+ s->output (midi_stream, i, ports_, moment_to_ticks (start_mom));
+ debug_output ("]", false);
+ }