If you have a choir score, or an orchestral score, where some voices are quiet
for a long time, you might want to hide staves containing nothing (or only
multi-measure rests). By default, LilyPond shows all staves, even if they
only contain rests. To change this into what is sometimes called a "French
Score" style, simply add the
\RemoveEmptyStaffContext variable, in a
\context block, to your
\layout.
The first system would still show all staves for all voices. To force this
setting to also apply to the first system of a score, set
remove-first of
VerticalAxisGroup to
#t.
If only one staff is displayed, the choir or the StaffGroup bracket would also be hidden, so you
will probably need to set
collapse-height of
SystemStartBracket to value 1 (or anything smaller than 5).
If you have some voices where you still want to display all (even empty) staves,
you need to set the remove-empty property
of the VerticalAxisGroup to #t for that
one staff only. You can do this in the
\with section of the staff (in this
example, the alto staff will never erase empty lines, while the soprano staff
will).