Documentation addition: instrument names for PianoStaff, GrandStaff, etc.

[Marcus Macauley]

I couldn't figure out how to add an instrument name to a GrandStaff, much less 
to a ChoirStaff or a StaffGroup. Kieren MacMillan (on lilypond-user) pointed me 
in the right direction, but the documentation could be updated to make this 
more obvious. So here is my suggestion for how to do it.

Append the following to "8.2.5 Instrument names" (before "See also" and "Bugs"):

-------------------
Instrument names may also be added to groups of staves, such as PianoStaff, 
GrandStaff, ChoirStaff, or StaffGroup.

For a PianoStaff, do something like:

\new PianoStaff <<
   \set PianoStaff.instrumentName = "Piano"
   \set PianoStaff.shortInstrumentName = "Pno"
   \new Staff {c1}
   \new Staff {\clef bass c1} >>

For a GrandStaff, ChoirStaff, or StaffGroup, the method is similar (simply 
replace PianoStaff with, for example, GrandStaff), but you also have to put a 
\context block like the following inside your score's \layout block:

   \context {\GrandStaff \consists "Instrument_name_engraver"}
---------------------

If you think it's appropriate, you could also mention, and perhaps link to, the 
"Tips and Tricks" file which demonstrates this for GrandStaff:

"instrument-name-grandstaff.ly"

which appears on this page,
http://lilypond.org/doc/v2.9/input/test/collated-files.html

and for which the source is here,
http://lilypond.org/doc/v2.9/input/test/lily-473581812.ly

...although it seems to me that an explanation in "8.2.5 Instrument names", as 
I suggested above, would make the foregoing "Tips and Tricks" file unnecessary.

Thanks, and keep up the good work!

Marcus Macauley


P.S. Unless there's a good reason not to, I think "Instrument_name_engraver" 
should be included in GrandStaff, ChoirStaff, and StaffGroup by default. If 
that were done, the extra step of adding, e.g.,
   \context {\GrandStaff \consists "Instrument_name_engraver"}
would become unnecessary.