The first part at 2:40 is just doubled and split L & R with a little flange. The next riff starts out in the center then I had him layer the second half an octave higher. I doubled the higher line (copy paste doubled, not 2 takes) and split them L & R, moved the left copy back 10ms and the right copy ahead 10ms. I use that trick all the time, mostly for vocals. I also had him give me the first note of the higher line and sustain it out with a little vibrato. Took that and flipped it backwards to fade into the octave part, again with the same stereo trick. Kinda sounds a little like feedback, I like it.