The wah-wah effect first appeared in the early 1900s when trumpet and trombone players found they could mimic the human voice by using the rubber part of a plunger to cover and uncover the bell of their horns (or their hand over the opening of a mute), effectively modulating the high end and resonant frequency of the horn’s sound.
Prototype incarnations of electronic wah-wah pedals appeared in the 1950s and were developed and released commercially in the 1960s. Although initially marketed to horn players, early recordings by Eric Clapton and Jimi Hendrix established the wah-wah as a mainstay effect for electric guitars. Coming full-circle, Miles Davis famously used a wah-wah pedal with his trumpet on the seminal album, “Bitches Brew,” and the funky rhythm guitar of Charles Pitts on “Shaft,” by Isaac Hayes, popularized the “wacka-wacka” sound.
Not to be outdone, bass players and keyboard players started using wah-wah effects on their instruments, as well.
Stevie Wonder defined and established a classic auto-wah Clavinet sound on his seminal song, “Higher Ground,” by using a Mu-Tron III Envelope Filter pedal. Rick Wright of Pink Floyd played a Wurlitzer through a wah-wah pedal in the song, “Money,” and jazz greats Herbie Hancock, Chick Corea, and Joe Zawinul, all used various wah-wah pedals on their Rhodes.
A standard wah-wah pedal (or software emulation) creates the effect by using a resonant filter that sweeps up and down in frequency. The frequency is usually controlled with a pedal or mod wheel, but it can also be controlled with an envelope follower that reacts to the volume of the input signal. The speed of the reaction can range from slow to very fast (faster than your foot!). Another method uses an LFO to modify the frequency of the filter’s resonance – the depth and speed of which is controllable.
A WAH-WAH / ENVELOPE FILTER section is used in the Patch, “Clavinet C – Wah Crunch.”
An envelope follower is used to create a wah effect that reacts dynamically to your playing.
Pedal, which is modulated by the Mod Wheel (CC#1) and Foot Controller (CC#4), opens the filter in the same way a wah-wah pedal does.
Sensitivity controls how much the cutoff frequency is triggered by velocity. If you want to control the cutoff with the Mod Wheel (CC#1) or a Foot Controller (CC#4), it is recommended to turn this down.
Shape controls the envelope attack time. Use higher settings for a slower attack.
Sweep Depth and Sweep Rate control the depth and rate of the LFO that is modulating the filter.
Gain controls the output level of the wah-wah.
An AUTO-WAH is used in the Patch, “Clavinet Pianet Duo – Auto-Wah.”
Here, an LFO is used to sweep the filter: Sweep Depth and Sweep Rate control the depth and rate of the LFO.
Frequency controls the cutoff frequency of the filter and Q controls the resonance or emphasis of that frequency.
The Mono button switches between a stereo or mono effect. When Mono is OFF, the left and right modulation is inverted for a stereo effect.