Dynamics/hairpin range for Voice
Currently we can set hairpins and dynamics to apply to the staff, the part (like both staves if a piano) or the entire score.
Esp. for closed score SATB, but also in other situation it'd be useful to restrict hairpins and dynamics to the voice they got attached to.
To maintain backward compatibility with existing scores, in the corresponding enum we need to take care of keeping the values for STAFF, PART and SYSTEM the same, so either append VOICE to the end of that enum or insert it in front, but set it to -1. Logically it should be the first entry.
Support for playback would mean that we'd have to change velocity to be a property of voices rather than staves.