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
16 \context PianoStaff <<
17 \context Staff = "treble" {
18 \set PianoStaff.instrument = "Piano "
19 \set Staff.instrument = "Right " { c''4 }}
20 \context Staff = "bass" { \set Staff.instrument = "Left " \clef bass c4 }>>