make key signature invisible?

[Sterling Sympatico]

Hi folks,

Can one make a key signature invisible?  I have a piece that changes key
a few times and has piano, two vocal, and five percussion lines.  There
is a lilypond bug with spacing first note after key signatures when some
staffs do not use them (in this case the five percussion lines have no
key sig and the piano and voice lines do).  Instead of tweaking the lily
grob settings, can I make the percussion lines regular Staff's with a
key signature but "hide" the key sig?

Just curious.

Sterling MacNay