Gear Geek: Wah-Wah Pedals

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When wah-wah pedals were introduced in 1967, they had an immediate and lasting effect on the sound of popular music.

Of all the effects available to musicians, wah-wah is probably the most distinctive and most easily identified by nonmusicians. It''s usually associated with electric guitar—many classic Jimi Hendrix and Eric Clapton solos would be very different without it—but it''s frequently used for electric violin, bass guitar, electric piano, and Clavinet, and occasionally, even brass and wind instruments. In the right hands (or should I say feet?), wah-wah can be one of the most expressive and evocative effects that technology provides.

Several companies experimented with tone-shifting effects in the ''60s, and the innovative Thomas Organ Company, which first imported Vox amps and instruments to the U.S., developed and patented the wah-wah pedal. In late 1966, Thomas engineer Brad Plunkett mounted a transistorized mid-range boost circuit whose frequency was controlled by a potentiometer in the housing of a Vox Continental organ''s volume pedal. One of his coworkers played a guitar through it, and voilà, wah-wah was born. The company''s CEO decided that marketing efforts should target sax and trumpet players rather than guitarists, however. Vox''s original 1967 wah-wah had an image of big-band trumpet player Clyde McCoy—famous for a 1930s pop song on which he used a “high-hat” mute for a similar effect— printed on the bottom plate.

Fortunately, others within the company recognized its potential as a guitar effect, and Plunkett continued tweaking it for electric guitar. Someone at Thomas Organ apparently thought the effect sounded like a baby crying and came up with the brand name Cry Baby. No one bothered to trademark the name, however, and Cry Baby pedals from a variety of manufacturers followed. Rock guitarists popularized the sound, and soon wahwahs were being made by Vox, Foxx, Maestro, Morley, DeArmond, Dunlop, Boss, Budda, Fulltone, and most major guitar and amp manufacturers.

Wah-wah pedals work by manually sweeping a bandpass or lowpass filter''s resonant peak, dynamically changing the signal''s spectral content. You create the classic wah-wah sound by rocking the treadle either rhythmically or synchronized with picking your guitar strings for a sound that resembles vocal phrasing. You can also achieve a vowellike tone by positioning the treadle somewhere in the middle of its range to simulate a formant by emphasizing a particular frequency band. Strumming muted guitar strings while pumping the treadle has driven the hook of many a funk track, too.

Although wah-wah pedals are ideal for sweeping synth sounds with your foot, you could achieve a similar effect by assigning a MIDI expression pedal to control a resonant filter''s frequency. Most guitar-amp-modeling plug-ins for DAWs include a wah-wah in their arsenal of virtual stompboxes. Wah aficionados insist that different makes have their own personalities, and indeed, an assortment of design types yield different but similar effects. On stage or in the studio, as with any kind of vintage instruments or effects, purists insist that nothing beats the real thing.

This is the final installment of “Gear Geek.” Synthesist, bassist, composer, and former EM senior editor Geary Yelton lives in Asheville, N.C.