The Angel Experiment (Maximum Ride, Book 1)

Envelope Filter

Envelope Filter is a sort of automatic wah wah. It wahs the tone more depending on the attack (how hard you pluck the string). Sounds funky. Jerry Garcia used one a lot on guitar. Flea uses one on bass.

Sounds very similar to wah wah. Maybe "Narcolepsy" by Third Eye Blind.

NOTE

You can buy, or if so inclined, make, a purely mechanical pedal with a rocker that can control (with a break cable type attachment) any knob on any other pedal.