I've implemented "chordmode" for Payasan patterned after LilyPond's chordmode.
Chordmode is intended as an intermediate layer for working with chords - LilyPond's chordmode is a bit inscrutable at some points and I believe I have a simpler representation for building and manipulating chords.
The implementation points to quite a few horrors in the module organization of Payasan that I will need to address. I already have 70 modules in the src directory which is excessive and I'll have to do something about combining some of them.