Hey ML,
I asked a similar question on the Music Practice & Theory Stack Exchange site, and I was told that the idea of changing clef automatically is - in most cases - a bad idea, at least musically/practically speaking. Nevertheless, I would like to ask for pointers as to how to accomplish this with pre-existing LilyPond capabilities or just try to implement it myself -- I am not at all familiar with the codebase.
The ideal situation would be that there's some kind of \clefAutoChange or similar command, and a mechanism to override the changing points would also be provided. This also needs to work for \transpose'd music. For example, a cellist told me that when there's a passage that lingers long enough above E1 (but not too much above A1 or so), the music is usually written with the tenor clef. A similar rule (of thumb) applies to viola music and its use of the treble clef, bassoon music etc.
Any pointers or thoughts on this?
Thank you,
-Elmo