The part and part-group abbreviations, on the first system also for a single staff.
The part and part-group names on the first system, their abbreviations on later systems.
On the first system, the part and part-group names on two lines where that makes them narrower, e.g. "Clarinet" / "in B♭".
No labels.
Which labels [[MusicSystem.createMusicSystemLabel]] creates left of a system's staves.