There are a handful of specific music references peppered throughout ALL of the Material and, consequently, are hard to find unless one has notated them over the years.
One thing I do remember is Seth referred to music as the least camouflaged form in physical reality and, thusly, the most powerful; also, when someone connects with a particular piece of music, it opens up paths to their inner self and refreshes them as such.
He did say about art, in general, that it is a touchstone to inner reality...