- Finding rests within beam runs. Not yet handling rests that are part of a tuplet but are at the start or end.
- Throwing assert if a voice disappears mid bar (but on a beat) without a rest at the start of the next beat.
- Starting on grace notes. For now I just need to match them up to owning stems. Need to handle beamed grace notes, grace notes that appear at the end of a line (attached to note on next line) and grace notes that appear twice (end of line and start of next line).
- It'd be useful to have note pitches for this. I might start that now instead.
- Finding clefs. Clefs used to be associated with notes. I guess that still makes sense. I'll associate them with staves and all stems played immediately after clef change.
- I'll only associate them after voices are done, so it'll be a slow(ish) search each time before that (done, not too slow).