Overdrive (óvərdrɑ̀yv) is the sound of a tube amp being pushed to its volume limit. The sound of an electric guitar through an overdriven tube amp being pushed to distortion is one of the cornerstones of rock and blues music. In its original form, the sound was achieved by cranking the volume full up and pushing the amp to its limit. While this method does produce the desired grind and singing overtones when playing, the volume levels are often excessive within the confines of a small performance, rehearsal or residential space. In order to achieve this sound at lower sound pressure levels, overdrive pedals were invented to simulate an overdriven amp.

Unlike distortion or fuzz, overdrive retains more dynamic range and does not quite boost the guitar’s signal as excessively. A good overdrive will preserve the fundamental sound of the guitar and amp while replicating that volume cranked tone without sounding like an external effect.