optional notes

[David Roundy]

I was wondering if there is a way in lilypond to put optional notes in
parentheses? 

This is very common in bell choir music, for low notes (or octave
doublings) that are good if you have enough players, but not really
necesary.  I imagine that one would just have to define another note
head style, but I have no idea how one would do this.

Thanks.

David Roundy