There's a lot of controversy about it. It's all bullshit, though. What happened is the backing keys are on DAT. That DAT is probably a Tascam DA-30MkII. or Panasonic SV-3700. Both of them have a tiny, unguarded, easy-to-bump-by-accident switch that switches from 44.1 to 48kHz. The keys were recorded at 44.1. The switch got bumped. The keys play back at 48. Now one part of the song is three and a half semi-tones sharp - if "Jump" is in A, Eddie now has to play it in Bflat and a half. So what you're hearing is Eddie going WTFKEYISTHIS?????? and trying to play up a note and then using the whammy to bend it into place. Meanwhile he's running around shouting at his guitar tech to fucking tune him an axe into whatever unholy key they happen to be playing. All the while the rest of the band are soldiering on - David is singing to the keys, Alex don't care and the bass is notably off. Good on 'em for trying because sweet jesus, they're in a pickle.