Hi MO,
I don’t understand LilyPond yet (and maybe never will…) with all its files but trying to. I am not sure if anything else will break if I make my own language settings file.
You may edit the file define-note-names.scm at your leisure - maybe there's trouble ahead if you try to use special characters like \ in a note name, but simply renaming all notes in one language, deleting some languages or adding new ones won't break anything.
But you're absolutely right - LilyPond is a _very_ complicated system that's really hard to understand in all its details. But the modular design makes it possible to tweak LilyPond's behaviour very much in one area without causing an avalanche of side-effects.
Lukas
