This is fairly crazy pedal and definitely not for everyone! It uses a 567 Tone Decoder chip. They were used for old telephony stuff, detecting/deciphering the frequencies of dial tones and routing calls. It's being dreadfully misused here to create a ring modulator, and overdiven to produce gnarly glitchy mayhem/ robotic modem sounds. The filter knob ("Fizz") gives a very satisfying sweep, allowing for pinpoint tone control, while the "Dry" knob lets you dial it back to reality a bit with a clean blend, or go all out on the chaos