The Little Big Muff Pi from Electro-Harmonix is a harmonic distortion-sustain pedal for the electric guitar player. The Little Big Muff Pi is identical to the Big Muff Pi, but in a compact, smaller die-cast chassis. This pedal features Sustain, Tone, and Volume controls. The Footswitch toggles between effect and bypass modes. A 9V battery is included with the unit and an optional 9.6 VDC-200BI power supply is available.