Urs Liska wrote
Step out of the dark and tell the world what we do!
I use LilyPond for alternative music notation systems like Clairnote:
http://clairnote.org/
http://clairnote.org/sheet-music/
and TwinNote (which was my previous focus):
http://clairnote.org/twinnote/
http://clairnote.org/twinnote/sheet-music/
I don't know if this qualifies for a ponding since it is a marginal use case
and I suppose there's a rationale for keeping the focus on more
mainstream/established uses. On the other hand, it does illustrate the
great flexibility and extensibility of LilyPond.
-Paul