can I force the KeySignature to display when a new clef requires it?

[Kieren MacMillan]

Hi all,

Yet another situation (see thread 
http://lists.gnu.org/archive/html/lilypond-user/2015-04/msg00274.html) where I 
want to force a grob to appear, but can’t seem to find a way to do it…

I have a percussion staff containing music for a single player who switches 
between pitched and unpitched instruments. Gould confirms my intuition/desire 
in this case: “A key signature must be added if a treble or bass clef is 
introduced for a new instrument after a non-pitched percussion clef” (pg. 276).

However, while I can easily \hide (or \omit) the KeySignature when the 
instrument is unpitched, I can’t seem to force the KeySignature to appear when 
the clef changes to a “pitched clef”. As with the thread mentioned above, I’d 
rather not add a \key \default to the content, since this is a 
presentation-layer issue that I would, if possible, prefer to solve in the 
presentation (edition-engraver) layer.

Any hints on how I can do this would be appreciated.

Thanks,
Kieren.
________________________________

Kieren MacMillan, composer
‣ website: www.kierenmacmillan.info
‣ email: address@hidden