The use of reverse audio in mainstream music really took off in the mid to late 1960s. However, to find the roots of this development we have to go back a bit further and consider a couple of significant changes. The first of these was the arrival of magnetic recording tape. This new medium and accompanying reel-to-reel machines revolutionised audio recording, and first found widespread use in broadcast and audio production in the 1940s and 1950s.
Significantly, the open deck design meant that by running the tape to the end and taking the right hand spool, turning it over and reloading it onto the left-hand side of the machine, you could play your whole recording backwards.