I have always loved that performance and did not know the backstory.
Also I love that somebody actually broke it down and is, as near as I can tell, exactly correct:
One correction -- I read further. The acts didn't run long, the band understood going in they would have 2 fewer minutes than the song runtime. They were used to doing it live faster than on disc but they'd never done it that fast. So they did practice beforehand, but then when the song started singer/yodeler Thijs van Leer surprised everybody by going even faster. You can see it register immediately with the drummer and then a measure later guitarist Jan Akkerman just says fuck it and accelerates even more. That's why by the end of the song van Leer actually has extra time to vamp -- they came in under.
I give the drummer so much credit because through the entire thing he's unflappable even with van Leer and Akkerman swerving back and forth between cadences trying to make each other break, but the drummer is always just knitting it back together. That's probably why when the song ends everybody on stage just nods at him as the hero of the night.
What a spectacularly wonderful and stupid and pointless and beautiful display of sheer joy.
I'd also like to note the drummer is chewing gum the whole time at a complete different time signature. Those guys' brains just don't work like ours.