+ void compress (Moment factor);
+
+ // Broadcast the event in a context's event-source.
+ void send_to_context (Context *c);
+
+ DECLARE_SCHEME_CALLBACK (duration_length_callback, (SCM));
+
+protected:
+ virtual SCM copy_mutable_properties () const;
+ virtual void type_check_assignment (SCM, SCM) const;
+ virtual void derived_mark () const;