From Death By Audio:
ENVELOPE FILTER WITH SERIOUS ATTITUDE
This mangled, filter-sweeping, abruptly overdriving pedal is designed to respond to your playing. It syncs its wave-thumping movement with the force at which you play. It multiplies dynamics into a hyper-exaggerated frenzy. It adds just the right amount of movement to punch through the mix and it reacts to an external trigger of your choosing to follow your tempo. Six selectable frequency ranges mean you're always gonna have just the right quack and oomph for whatever's plugged in! The sounds are wild, the thump is thick, and the animation is deep.