I could imagine two places.
https://music.stackexchange.com/
or
https://tex.stackexchange.com/
Therefore the question is, how much TeX-alike is Lilypond. I have the feeling, that I would get better answers on TeX.SX, but I wouldn't blame anybody to close questions for music-typesetting issues as off-topic.
What do you think? Is the TeX-comunity interested in this or should I try to find answers at Music.SX?