Point is, Fallout isn't all 50s like Bethesda makes it out to be.
It's what the 50's THOUGHT the future would be, as well as what the 80's THOUGHT the future would be. It's neither 80's nor 50's, but does reflect and represent a lot of the popular/pulp fiction of the future from those times. It basically means, like you said, we have NO IDEA what their music was like just before the war, BUT... an earlier post referred to why some of the surviving music present in the games was 50's might be due to the physical format of the preserved music, itself. The King mentions that his gang was inspired by Elvis music, but could not share any with the Courier because the
tapes had long since broken down. So clearly we may be able to assume that some cassettes made it some time after the Great War? But New Vegas is an exception when it comes to most Wasteland settlements, because it was sheltered from the nuclear blasts that struck most of the rest of the world, so some tapes surviving in a usable state until just prior to the 2280's in New Vegas doesn't mean that the same could be said of other places. But items found in vaults, perhaps? Beyond that, this also means that the vinyl records would have made it quite a while because they're physical blocks that held the music within their very shape. So, conceivably, music anywhere from the 30's to the 80's and possibly even 90's could be present in the time where the
Fallout games takes place.
As far as the
inspired music goes... that's the realm of the ambient tracks, which as I mentioned in my first posts here, are ALL that really matter. Whether they're reminiscent of Mark Morgan or Mark Morgan is once again tasked with the creation of the ambient tracks, either's fine. Just keep the radio songs
on the radio.
