As opposed to a distortion or fuzz pedal, an overdrive pedal does one of two things. It either recreates the sound of a cranked tube amplifier, especially a classic amplifier such as a Fender Bassman or Marshall JTM-45, or it can be used to push or (you guessed it) "overdrive" the front end of a tube amp so it produces a pleasing, smooth distortion. Another distinction between overdrive and distortion pedals is that overdrive pedals typically work better when the amplifier volume is turned up. A distortion pedal will produce the same sound regardless of the volume. With that in mind, it's always best to test overdrive pedals with a wide range of amp volumes so that you have a clear idea of the pedal's true capabilities. While it's impossible to list all of the influential guitarists who have used overdrive pedals, no better example exists than Stevie Ray Vaughan, who regularly used the original Ibanez Tubescreamers to overdrive his amplifiers.