The "remove everything but vocals" plugins usually just sum up the stereo channels, basically erasing everything but what's mixed in the middle. So they wouldn't work on for example The Beatles' albums where everything is in the middle (mono) or only left or right (the early stereo mixes).
But anyway, these are fun to listen to. And there are a LOT of these, here's just one channel:
https://www.youtube.com/channel/UCcI...KnAkzaZI0qc0aQ
Ice