Electric Wizard

Love Electric Wizard..Been listening to them for a while now..definitely one of my favorite riff heavy bands. I like covering their stuff because it's fun to play on guitar. While covering a song by them called Mourning Prayer I ran into a little trouble with one part and I wanted to see if anyone could pick out what it is exactly that the guitarist is doing... http://www.youtube.com/watch?v=kIidnlkyT2c it's the part from 2:45-3 something where each riff ends with a higher register "scream"..It's the "scream" that I'm having a hard time putting my finger on..what is he doing there exactly to produce that kind of sound? Thanks in advance..

-Nick