I imagine some of the music is triggered by what is going on. In the soundtrack files some of the filenames seem to indicate this (danger, discovery, etc), but it’d be nice to have something to slightly increase the frequency of idle music, I agree.
I love the music, it would be nice to be able to control the frequency of plays. I’ve ended up turning the music off and streaming music while I play. Sometimes you do repetitive tasks, and music makes all the difference.