Lilypond-book doesn't seem to understand the include structure very
well. That is, it's using the included files, but doesn't seem to
know that it needs to rebuild the snippets if you change an included
file. I'm working around this by removing all the snippets when I
change anything, but obviously this is going to be a problem with
In the past, I've worked around this by not using included files, but
I really want to be able to get score and parts from the same source.