So do the Fiends listen to music? I can't quite picture them listening to Sinatra. But as far as I know, there was no angry music, at all, pre-1970's. Maybe sad music, or anti-war, but not furious with rage.

It's my personal belief that music continued to be produced in the wasteland (because why not if the tech is still there? It's possible!) and even if it was passed down by musicians from one generation in a tribe to the next the original structure of the song would eventually be changed into different variations leading to new sounds, hence new music, if that makes sense (I didn't really know how to describe what I was thinking).

Anyways, good topic! I've always found that the lack of musicians in fallout was kind of odd, everyone can make music even if it is just tapping a pencil or clicking a pen. It's something that just kind of comes natural to almost anyone and everyone.

The Khans seem fairly civil and the fiends took a vault, so its certainly possible they've been exposed to music, but I suspect that raider-types would simply not be able to stand the happy, innocent pre-war music. If music got stunted some time in the 1960s, perhaps the raider-types would pick up where that left off -- they are certainly rebellious and not interested in conforming. That, I think, might start with 70's-ish psychobilly and punk covers of older songs.
The leaders of the fiends are not identical, each has a different personality. So there's room for a fiend or two who actually care about music. Violence, chaos and drugs do not inhibit music. I think there would be some real irony if the new music was coming from the uncivilized fiends.