there's this book "vaterland", i think, that is about some guy living in an alternate universe or something where the nazis won the war. i wonder if it mentions music, i haven't read it yet.
one can only speculate about what music would look like if we'd be living in such a world. i guess the radio would be full of prussian marches and german folk songs. most other music like rock wouldn't even have been developed, except maybe underground (there used to be underground jazz-clubs in germany during ww2.), but there could never have been music comparable to the stuff we have now.