An
effects unit (
effect box,
stomp box,
stompbox, or
pedal) is an
electronic device that
alters how a
musical instrument or other audio source sounds. Some effects subtly "color" a sound, while others transform it dramatically. Musicians use effects units during live performances or in the
studio, typically with
electric guitar,
keyboard, or
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.