Reversing a guitar solo is by now a common technique (one of the most prominent examples is George Harrison's solo in "I'm Only Sleeping"). However, John Petrucci of Dream Theater took this a few steps further.
Six Degress of Inner Turbulence was the sixth studio album by Dream Theater and it featured the song "Misunderstood". It has one of James LaBrie's finest performances and around the 4:40 mark starts Petrucci's guitar solo. It might not be very audible at first because even though it is reversed it still sounds like a very normal guitar solo. This is because Petrucci first played it, reversed the recording, then learned the reverse version. He recorded playing the reverse version, and reversed it once more (if you can keep up) to achieve the original version of the solo with twist on how the notes actually sound and their dynamics
It is truly mind-blowing when you realize this and listen to it again. We want to thank John Petrucci for bringing back the pretentious side of prog :)