Guitar effect

An effects unit or pedal is an electronic or digital device that alters how a musical instrument or other audio source sounds. Some effects subtly "color" a sound, such as a reverb unit used on a low setting, while others transform it dramatically, such as a distortion pedal set to its maximum level. Musicians use effects units during live performances or in the studio, typically with electric guitar, electronic keyboard, electric piano or electric bass. While most frequently used with electric or electronic instruments, effects can also be used with acoustic instruments, drums and vocals. Examples of common effects units include wah-wah pedals, fuzzboxes and reverb units.

Effects are built into amplifiers, housed in table top units, "stompboxes" and "rackmount units", or they are built into the instruments themselves. A stompbox or "pedal" is a small metal or plastic box placed on the floor in front of the musician and connected to the instrument and the instrument amplifier with patch cords. Typically, one or more on-off foot-operated switches control a device that provides only one or two effects, with many pedals having knobs for controlling the volume, tone and intensity of the effect. A rackmount device mounts on a standard 19-inch equipment rack and usually contains several types of effects.

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