Note.Free -- removes from tie, chord, beam, event, and selection, frees note
Chord.RemoveNote -- removes note from chord, frees chord if length < 2
Chord.Free -- removes chord from beam, removes notes from chord, frees chord
Beam.RemoveItem -- removes item from beam, frees beam if length < 2
Beam.Free -- removes beam from beam, removes items from beam, frees beam
Event.RemoveNote -- removes note from event, frees event if free = TRUE
Event.Free -- removes event from anything that points to it, frees event
Piece.RemoveEvent -- removes event from piece.  never frees piece
Piece.Free -- utterly destroys piece.

A note can be in at most one chord.
A chord can be in at most one beam.
Every note in a chord belongs to the same beam.
Every note in a chord belongs to the same sync.
IF n.beam # NIL THEN IF n.chord # NIL THEN n.chord is a part of the beam ELSE n is.