Philip Glass: How do they play it so fast?

I am constantly in awe of real musicians. This clip (wait a mo while it winds forward to 44:20) is 'The Grid' from Koyaanisqatsi, which could be the greatest music video ever made - certainly the most copied. Anyway, listening to the score the other morning, wondering how it was played - it starts out slow, then gets absurdly fast (at 47:40), and carries on for about 16 minutes without drawing breath. In search of visual evidence, I found this awesome clip of Philip Glass rocking the Prophet 5 in 1982, and this college band playing something from Glassworks. I can't imagine being able to do that. Don't your fingers really hurt? Doesn't your brain melt?