I guess you can’t just play the composition at normal piano speed and just slow it down however many percent, because organs aren’t like mellotrons in that it’s an acoustic instrument whose exact sound is always changing. Mellotrons can warble but in the end it’s still a short tape loop, and they don’t have the decay of a piano.

Is there someone physically holding down the organ key for two-and-a-half years at a time, just swapping out organists while keeping the key depressed? Or do they use a paperweight or something? They say it’s non-computerized.

John Cage was into gimmicks like this, btw.