+/*
+
+ TODO: handling of grace notes is exquisite pain. This handling
+ should be formally specified and then the implementation verified.
+
+*/
+
+/*
+
+ TODO: the grace note handling hasn't been done for skip() and
+ get_music(), meaning that staff-switching and partcombining will be
+ broken with grace notes.
+
+ */
+/*
+
+ TODO: the grace note handling hasn't been done for skip() and
+ get_music(), meaning that staff-switching and partcombining will be
+ broken with grace notes.
+
+ */