The artifact colours are quite off as well, so I suspect the card used was not a real IBM CGA card. On my ATi Small Wonder and Paradise PVC4 cards, I get the ex

The artifact colours are quite off as well, so I suspect the card used was not a real IBM CGA card. On my ATi Small Wonder and Paradise PVC4 cards, I get the exact same Kefrens bars, with the top chopped off. Having said that, the fact that the music slows down noticeable during the moire-effect seems to indicate that indeed some instructions are a few cycles off here and there.