Mullein

Copperbox revision 567.

As the last couple of days work on interfacing Haskore and Mullein wasn't satisfactory, I'm considering a different approach - make Mullein scores more like Haskore.

This has the obvious disadvantage that a composition in Haskore will need porting to Mullein, but the alternative where I try to reconstruct structure (such as chords) from Haskore to build a Mullein score programmatically seems like a dead-end.