There should be a clear separation between the Tracklist and the Mixer. The Tracklist should be concerned with Tracks in the arranger, and the Mixer should be concerned with Channels, routing and Port connections.
- Track* tracks
- All tracks that exist.
- Track* chord_track
- The chord track, for convenience.
- Track* marker_track
- The marker track, for convenience.
- Track* master_track
- The master track, for convenience.
- TracklistWidget* widget
- Non-pinned TracklistWidget.
- PinnedTracklistWidget* pinned_widget