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.