grely: wip towards really translating gabc to lilypond
lygre: wip concerning conversion of gabc 'visual pitch' to absolute pitch
Note#diatonic_steps works as expected, but there is an unwanted mysterious octave correction
Scale explored by specs

I haven't noticed before that Scale#degree copes with degrees over the range of an octave.
So the computations in Note#diatonic_steps could probably be simplified.