I thought Three Dog said he found records at the GNR studio, and that explains why he plays the same dozen songs over again.
Maybe the same thing can be said about the New Vegas stations. Only a dozen songs survived 200 years after the war.
I always figured not much music survived the bombs, but I think that would mean that whatever did survive was shared (or re-recorded from airplay) pretty quickly.
Three Dog, at the very least, doesn't strike me as the guy that isn't going to share. Music is one of the better artifacts of the good in humanity. For that reason, I think the Fallout music catalog should only get bigger, and I would welcome the day that we actually find old music recordings while scav'ing ruins and vaults only to share (or trade) them to interested parties. THAT would be something to collect, even as cool as the bobbleheads were.