The wah-wah audio effect is incredibly expressive. Its associated with whole genres of music, and it can be heard on many of the most influential funk, soul, jazz and rock recordings over the past 50 years.
Jimi Hendrix would sometimes use the wah-wah effect while leaving the pedal in a particular location, creating a unique filter effect that did not change over time. However, in ‘Voodoo Child (slight return)’, Hendrix muted the strummed strings while rocking the pedal, creating a percussive effect. The sweeping of the wah-wah pedal is more dramatic in the louder versus and the chorus, emphasizing the song’s blues styling.
The ‘wacka-wacka’ sound that Hendrix created soon became a trademark of a whole subgenre of 1970s funk and soul. Melvin ‘Wah-Wah Watson’ Ragin, a highly respected Motown session musician, is renowned for his use of the wah-wah pedal, especially on The Temptations ‘Papa Was A Rolling Stone’. This distinctive ‘wacka-wacka’ funk style of soon became a feature of urban black crime dramas, such as in Isaac Hayes’ ‘Theme from Shaft,’ Bobby Womack’s score to ‘Across 110th Street’ and Curtis Mayfield’s ‘Superfly.’
Another unusual use of the wah-wah pedal can be heard on the Pink Floyd song ‘Echoes.’ Here, screaming sounds were created by plugging in the pedal back to front, that is, the amplifier was connected to the input and he guitar was connected to the pedal’s output.
Of course, use of wah pedals is not reserved just to guitar. Bass players have used wah-wah pedals on well-known recordings (Michael Henderson playing with Miles Davis, Cliff Burton of Metallica, …). John Medeski and Garth Hudson use the pedals with Clavinets. Rick Wright employed a wah-wah pedal on a Wurlitzer electric piano on the Pink Floyd song ‘Money,’ and Dick Sims used it with a Hammond organ. Miles Davis’s ensembles used it to great extent, both on trumpet and on electric pianos. The wah-wah is frequently used by electric violinists, such as Boyd Tinsley of the Dave Matthews Band. Wah wah pedals applied to amplified saxophone also feature on albums by Frank Zappa and David Bowie.