Anything which has length or pitch
Anything which has length or pitch.In Lily, everything that can be thought to have a length and a pitch (which has a duration which can be transposed) is considered "music",
Music is hierarchical:
This program documentation comes from lilypond-1.0.0.tar.gz. It was generated by <janneke@gnu.org> on Fri Jul 31 15:42:17 CEST 1998