In setting an a apella SATB piece and the (generated) rehearsal
piano part, I would like to create two PDF files with different
linebreaks.
Each part has many occurrences of a variable "midBarBreak" defined as
{ \bar "" \break } so as to break up the vocal lines at the end of
the lines of the set verse. This works just fine.
Unfortunately, lilypond seems to process variables upon first reading
them, so I can't use the old TeX trick of \let \this \that; nor does
\noexpand have a lilypond cognate that I can find. Nor yet do I see
any way to incorporate logic into the variable (e.g., if in
ChoirStaff, break; if in PianoStaff, ignore). I suspect it's there,
somewhere, but I'm not enough of a schemer to see how to use, e.g.,
ly:context-parent.
So, since TeXish methods don't work, I thought I'd ask if there's a
lilypondish way to do this.