printing a tiny pianostaff at the beginning of a score

[Sandro Santilli]

I'd like to leave some indications (rythmic, mostly)
for bass and guitar at the start of a piece. Right now
I'm doing this with a pencil, but I'm wondering how
to do it with lilypond. It could be a smaller PianoStaff,
on a line by itself. How could this be done ?

Thanks in advance

--strk;