4 Staff margins are also markings attached to barlines. They should be
5 left of the staff, and be centered vertically with respect to the staff.
6 They may be on normal staves, but also on compound staves, like the
21 \context PianoStaff <<
22 \context Staff = "treble" {
23 \set PianoStaff.instrument = "Piano"
24 \set Staff.instrument = "Right" { c''4 }}
25 \context Staff = "bass" {
26 \set Staff.instrument = "Left"