@mcc When I was young, a friend and I kind of did this, but the first track of The Downward Spiral recorded on top of itself. Two boomboxes, one with a dual tape deck where you could play both tapes at the same time (we may have had to hold both play buttons down for this to work, memory is fuzzy).

Then dub the first song onto two tapes, put those in the first boombox, line out into the second, record that on one tape. Swap that into the first boombox and repeat. Swap that into the second deck of the first and repeat.

Things got muddy and distorted quickly, but the neat part was that the decks ran at slightly different speeds, either due to battery level or different mechanism or whatever. So the earlier stuff got slower with every generation.

@ieure My friend had a theory that "Kid A" was designed to sync up to a movie that had not yet been discovered*. After Amnesiac came out I developed an alternate theory** It was meant to sync up with Kid A. I tried playing the two simultaneously. The theory did not bear out

* He based this on a quote in an interview from Johnny Greenwood saying that he wanted to score a movie. Turned out Johnny Greenwood just wanted to score a movie.

** Based on some bridges of unusual length in both albums