Tremolo

A tremolo effect produces a slight, rapid variation in the volume of a note or chord. Tremolo effects normally have a "rate" knob which allows a performer to change the speed of the variation. The "tremolo effect” should not be confused with the misleadingly-named "tremolo bar", a device on a guitar bridge which allows the player to create a vibrato or “pitch-bending” effect. The guitar intro in the Rolling Stones' "Gimme Shelter" features a tremolo effect.