I'm getting confused. Some of the replies seem to be conflating the
three meanings of "language" that might be meant here.
1) the note names, as in \key fis \major
2) the text printed on the diagram, as in \combine \move-markup "es/dis"
3) the variable names in the code, as in (let* ((mittel (mittel-punkt
stencil))
1 is always dutch, isn't it.
3 depends on who's writing the code. It
gets a bit inconvenient if it has a lot of non-ascii names in it
(especially when attachments' charsets don't match the email headers).
So 2 is the substantial one, isn't it. Presumably LP and scheme know
what the current language setting is, so they could use a lookup table
based on that. (Presumably there must be such a table buried in LP).
That way, any language would be selectable by running ly over the
snippet's code and running LP on the output.