Pinch harmonic

A pinch harmonic (also known as squelch picking, pick harmonic or squealy) is a guitar technique to achieve artificial harmonics in which the player's thumb or index finger on the picking hand slightly catches the string after it is picked, canceling the fundamental frequency of the string, and letting one of the harmonics dominate. This results in a high pitched sound which is particularly discernible on an electrically amplified guitar as a "squeal".

The technique is possible on any fretted stringed instrument, but is most widely employed by electric guitarists, especially in heavy metal and rock music where heavy distortion ensures that the otherwise subtle harmonic is greatly amplified. An early example can be heard in Roy Buchanan's 1962 recording of "Potato Peeler".Robbie Robertson, who learned the technique from Buchanan, used the technique, as did Leslie West.

A guitarist of the rock genre widely known for his use of pinch harmonics is Billy Gibbons of ZZ Top, who uses them frequently in guitar solos, an example being the second solo on the well-known "La Grange".

Another exponent of this technique was Irish blues rock guitarist Rory Gallagher, as in the track "Walk On Hot Coals" from the album Irish Tour '74.

Artists such as Eddie Van Halen, Joe Satriani and Steve Vai made the technique popular, utilizing the tremolo arm and high gain amps together with the pinch harmonic to produce horse-like wails from the instrument.

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