I doubt they are using ACTUAL recordings of bands - not least because sampling them and splicing them and editing them and overwriting them would be too much like hard work for whoever's making them.

Instead, they can just type in AI prompts to software such as Suno, which has trained itself on the aggregate sum total of all the millions of 1940s/1950s recordings out there. So no direct copyright infringement of any one particular singer or band.