So no coder is getting the copyright back on his corporate code. Similarly, almost no film or tv writers will get their copyrights back. Nor will most musical acts from the more-modern era. (Somehow, dead tree publishing isn't built on 'work for hire' contracts. So this will likely let many print authors renegotiate.)
Anyway, starting around the late 80s labels required recording artists to sign the same sort of farcical 'work for hire' contract that other authors are forced to sign.
("yeah, I wrote this while I was being paid a salary, receiving health benefits and all that jazz. I certainly wasn't building it over the last three years of working two jobs, playing dive bars and eating baloney-on-hand. I just met you yesterday, sign this contract today and it springs fully-formed from my head tomorrow -- just for you and without any of those pesky W2s or insurance forms.")
That's why the music industry didn't push too hard to get these old recordings covered -- it's a temporary blip, not a threat to their current model.