Auto-wah is a type of wah-wah effects pedal typically used with

electric guitar An electric guitar is a guitar that requires external electric Guitar amplifier, sound amplification in order to be heard at typical performance volumes, unlike a standard acoustic guitar. It uses one or more pickup (music technology), pickups ...

bass guitar The bass guitar (), also known as the electric bass guitar, electric bass, or simply the bass, is the lowest-pitched member of the guitar family. It is similar in appearance and construction to an Electric guitar, electric but with a longer nec ...

, clavinet, and electric piano etc. The distinctive choppy rhythm guitar sound on many

funk Funk is a music genre that originated in African-American communities in the mid-1960s when musicians created a rhythmic, danceable new form of music through a mixture of various music genres that were popular among African-Americans in the ...

and

disco Disco is a music genre, genre of dance music and a subculture that emerged in the late 1960s from the United States' urban nightclub, nightlife, particularly in African Americans, African-American, Italian-Americans, Italian-American, LGBTQ ...

recordings from the 1970s popularized the effect.

Terminology

The effect is also known as a "Q-wah", "T-wah", "envelope following filter", "envelope follower" or "envelope filter".

Operation

Instead of the effect being controlled by a foot-operated treadle pedal, as on a standard wah-wah, the effect alters in response to the volume of the input signal.''The Boss Book: The Ultimate Guide to the World's Most Popular Compact Effects for Guitar'', 2002, Hal Leonard Corporation Like a wah, it works by adjusting the central frequency of a peaking filter, which amplifies a specific frequency and cuts off other selected frequencies. Since the electronic circuits in the effect can respond much faster than a human musician can physically move a pedal, certain effects that a standard wah cannot achieve are only possible with auto-wah. The response of the effect is highly interactive with the dynamics of the input signal - this makes it possible to vary the response at will via slight adjustments to playing technique. Therefore, it may take some practice before the response of the auto-wah can be wilfully controlled in order to achieve a consistent sound. A typical auto-wah circuit uses an

envelope detector An envelope detector (sometimes called a peak detector) is an electronic circuit that takes a (relatively) high-frequency signal as input and outputs the '' envelope'' of the original signal. Diode detector A simple form of envelope detect ...

to produce a voltage representing the overall volume of the input. This signal is then used to sweep the cutoff frequency of a filter. The filter usually has a

low-pass A low-pass filter is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. The exact frequency response of the filter depends on the filt ...

or bandpass response. The Boss AW-3 is an example of such a device. There is a variant of auto-wah that utilizes a low-frequency oscillator (LFO) instead of an envelope detector to alter the effect. The filter response varies constantly with time and is not linked to playing dynamics. The Boss AW-2 is an example of such a device. The difference in sound is subtle, but careful listeners will notice the constant period of the filter sweep. The song "Falling Into Grace" by the

Red Hot Chili Peppers The Red Hot Chili Peppers are an American rock band formed in Los Angeles in 1982, consisting of Anthony Kiedis (vocals), Flea (musician), Flea (bass), John Frusciante (guitar), and Chad Smith (drums). Their music incorporates elements of a ...

is an example of an LFO controlled auto-wah applied to the bass guitar. Typical controls on an auto-wah include a sensitivity control to adjust the input level to match the level expected by the envelope follower and other circuitry, a control for the initial cutoff point of the filter, and a control for the depth of the filter sweep. Some more sophisticated units offer controls for the resonance of the filter, multiple filter types, and options for sweeping the filter up or down.

Notable examples

The first envelope-controlled filter built for musical instruments was the Mu-Tron III, invented by Mike Beigel. Other examples include the MXR Envelope Filter and the Boss AW-2 Auto Wah (LFO controlled).

Grateful Dead The Grateful Dead was an American rock music, rock band formed in Palo Alto, California, in 1965. Known for their eclectic style that fused elements of rock, blues, jazz, Folk music, folk, country music, country, bluegrass music, bluegrass, roc ...

guitarist Jerry Garcia is known for extensive use of an envelope filter (particularly the Mu-Tron III), examples being his playing on "Estimated Prophet" and " Shakedown Street".

Phish Phish is an American rock band formed in Burlington, Vermont, in 1983. The band consists of guitarist Trey Anastasio, bassist Mike Gordon, drummer Jon Fishman, and keyboardist Page McConnell, all of whom perform vocals, with Anastasio being the ...

guitarist Trey Anastasio also frequently uses the effect, especially in addition to the use of distortion. The guitar solo in " What I Am" by Edie Brickell & New Bohemians features an auto-wah effect.

J Mascis Joseph Donald Mascis Jr. (born December 10, 1965), better known as J Mascis, is an American musician who is the singer, guitarist and main songwriter for the alternative rock band Dinosaur Jr. He has also released several albums as a solo artist a ...

became well known for the use of the effect thanks to his role as guitarist in the group Dinosaur Jr.

References

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