Here's the Compactotron C-2 in use. It's a distortion circuit followed by a low pass filter, the cut-off frequency determined by the 'freq' knob or the Igor pressure pad. The Heel Switch drops the cut-off down to nothing momentarily. It doesn't matter how long or hard you press the Heel Switch; one press makes one trigger, the length of the drop decided by the 'release' knob. The 'Q' switch on the top changes the sound from a wah-like sound - with the guitar coming through - to a round synth-like throb. The 'rate' and 'depth' controls adjust an oscillator that modulates the cut-off frequency up and down.