i use a boss ps-5 super shifter, which has an expression pedal input. the (44-page-long) manual says you can only use some specific roland expression pedal, but i use a moog ep-1 with it and it works fine. very very cool sounds, the ps-5 honestly tracks better than the whammy. you can also use it as a volume boost by rocking the expression pedal all the way back. this thing has honestly kicked my murf off the board because i find way more use for it. my only gripe with it is that i play tuned to Eb so it's kind of hard to use the harmonizer.