The classic Big Muff Pi is perhaps the most widely-used fuzz pedal ever built, and the Electro-Harmonix Deluxe Bass Big Muff Pi adds a new world of control and a deep frequency response tailored specifically for bass guitar. Dial in the crossover controls to hone in your tone, blend the dry signal back in for more impact, and bring the built-in gate to the party if you've got absurd amounts of gain happening and don't want any feedback.