I wrote a music typesetter when I was about fifteen, and revised it five years later so it didn't crash all the time. It isn't world-class, but it did mean that I had already stolen a decent set of musical symbol outlines from somewhere, so when I thought "now where can I find a treble clef" my first thought was to use the one I already had rather than Google.

(Also, being an outline description, it had the useful advantage of being able to scale conveniently to precisely the size I wanted. Unfortunately, it proved very hard to deal with the aliasing issues...)