A Wah-wah pedal is a foot-operated pedal, technically a kind of band-pass filter, which allows only a small portion of the incoming signal’s frequencies to pass. Rocking the pedal back and forth alternately allows lower and higher frequencies to pass through, the effect being similar to a person saying “wah”. The wah-wah pedal, used with guitar, is most associated with 1960s psychedelic rock and 1970s funk. During this period wah-wah pedals often incorporated a fuzzbox to process the sound before the wah-wah circuit, the combination producing a dramatic effect known as fuzz-wah.
Some wah-wah pedals include
Dunlop Cry Baby (repeatedly stated as being used by the late Jimi Hendrix, which is not entirely true. Jimi used VOX and Cry Baby wah-wah pedals but mostly used a VOX V848 Clyde McCoy Wah Wah which can be heard on Voodoo Child (Slight Return)
VOX V847 Wah Wah