This is the Digitech whammy for guitar. It's basically a pitch shifter connected to a wah. It can be used to do nice jumps or crazy pitch bending stuff. It has a very distinct sound compared to other effects pedals. You probably already know what it does though if you're here. Used by artists like Tom Morello, Matt Belamy, Jack White and more. Very cool thing. This can ONLY be used with this power supply. It will not have enough power on the standard 9v.