An effects unit or effects pedal is an electronic or digital device that alters the sound of a musical instrument or other audio source. Common effects include distortion/overdrive, often used with electric guitar in electric blues and rock music; dynamic effects such as volume pedals and compressors, which affect loudness; filters such as wah-wah pedals and graphic equalizers, which modify frequency ranges; modulation effects, such as chorus, flangers and phasers; pitch effects such as pitch shifters; and time effects, such as reverb and delay, which create echoing sounds and emulate the sound of different spaces.Most modern effects use solid-state electronics or computer chips. Some effects, particularly older ones such as Leslie speakers and spring reverbs, use mechanical components or vacuum tubes. Effects are often used as stompboxes, which are typically placed on the floor and controlled with footswitches. They are also built into amplifiers, tabletop units designed for DJs and record producers, and rackmounts, and are widely used as software VSTs.
Modern digital effects utilizecomputer chips to emulate an array of sounds. All of the aforementioned effects have been recreated with digital, and the realm of potential has been expanded dramatically with the increase in technologies. Specially areas like reverb and delay have greatly benefited from this advancement. Certain reverb effects now have the processing power to emulate a variety of spaces.
Musicians, audio engineers and record producers use effects units during live performances or in the studio, typically with electric guitar, bass guitar, electronic keyboard or electric piano. While guitar effects are most frequently used with electric or electronic instruments, effects can also be used with acoustic instruments, drums and vocals.