Um... you guys are all wrong. It only sounds symetric because you haven't heard the intro enough times to actually understand what's going on there with the notes the two are playing. I don't claim to think that I know, but I can tell it's not the same melody backwards as forwards. Just sounds that way because every Tool song uses the same 5 goddamn notes these days, it seems... patient, schism, now this. Silly regurgitators...