sigc::signal<void, Track &> signal_track_added;
sigc::signal<void, Track &> signal_track_removed;
sigc::signal<void, Route &> signal_route_added;
sigc::signal<void, Route &> signal_route_removed;
sigc::signal<void, Track &> signal_track_added;
sigc::signal<void, Track &> signal_track_removed;
sigc::signal<void, Route &> signal_route_added;
sigc::signal<void, Route &> signal_route_removed;