sigc::signal<void, unsigned, Track *> signal_link_changed;
sigc::signal<void, unsigned> signal_path_changing;
sigc::signal<void, unsigned> signal_path_changed;
sigc::signal<void, unsigned, Track *> signal_link_changed;
sigc::signal<void, unsigned> signal_path_changing;
sigc::signal<void, unsigned> signal_path_changed;