Distortion (music)

Distortion and overdrive are forms of audio signal processing used to alter the sound of amplified electric musical instruments, usually by increasing their gain, producing a "fuzzy", "growling", or "gritty" tone.

Guitarists playing electric blues originally obtained an overdriven sound by turning up their vacuum tube-powered guitar amplifiers to high volumes, which caused the signal to distort.

[1] The effects alter the instrument sound by clipping the signal (pushing it past its maximum, which shears off the peaks and troughs of the signal waves), adding sustain and harmonic and inharmonic overtones and leading to a compressed sound that is often described as "warm" and "dirty", depending on the type and intensity of distortion used.

[2] Fuzz is a particular form of extreme distortion originally created by guitarists using faulty equipment (such as a misaligned valve (tube); see below), which has been emulated since the 1960s by a number of "fuzzbox" effects pedals.

The first guitar amplifiers were relatively low-fidelity, and would often produce distortion when their volume (gain) was increased beyond their design limit or if they sustained minor damage.

[6] Later, around 1945, Western swing guitarist and member of the Bob Wills band, Junior Barnard, began experimenting with a rudimentary humbucker pick-up and a small amplifier to obtain his signature "low-down and dirty" bluesy sound which allowed for more "fluid and funky" chords.

[6] Many electric blues guitarists, including Chicago bluesmen such as Elmore James and Buddy Guy, experimented to get a guitar sound that paralleled the rawness of blues singers such as Muddy Waters and Howlin' Wolf, replacing often their originals with the powerful Valco "Chicagoan" pick-ups, originally created for lap-steel, to obtain a louder and fatter tone.

[8][9][10] In the early 1950s, guitar distortion sounds started to evolve based on sounds created earlier in the decade by accidental damage to amps, such as in the popular early recording of the 1951 Ike Turner and the Kings of Rhythm song "Rocket 88", where guitarist Willie Kizart used a vacuum tube amplifier that had a speaker cone slightly damaged in transport.

[14] Electric blues guitarist Willie Johnson of Howlin' Wolf′s band began deliberately increasing gain beyond its intended levels to produce "warm" distorted sounds.

[15] Chuck Berry's 1955 classic "Maybellene" features a guitar solo with warm overtones created by his small valve amplifier.

[16] Pat Hare produced heavily distorted power chords on his electric guitar for records such as James Cotton's "Cotton Crop Blues" (1954) as well as his "I'm Gonna Murder My Baby" (1954), creating "a grittier, nastier, more ferocious electric guitar sound," accomplished by turning the volume knob on his amplifier "all the way to the right until the speaker was screaming.

[19] In the late 1950s, Guitarist Link Wray began manipulating his amplifiers' vacuum tubes to create a "noisy" and "dirty" sound for his solos after a similarly accidental discovery.

Wray also poked holes in his speaker cones with pencils to further distort his tone, used electronic echo chambers (then usually employed by singers), the recent powerful and "fat" Gibson humbucker pickups, and controlled "feedback" (Larsen effect).

[20] In 1961, Grady Martin scored a hit with a fuzzy tone caused by a faulty preamplifier that distorted his guitar playing on the Marty Robbins song "Don't Worry".

[22][23][24] Shortly thereafter, the American instrumental rock band The Ventures asked their friend, session musician and electronics enthusiast Orville "Red" Rhodes for help recreating the Grady Martin "fuzz" sound.

[25] In 1964, a fuzzy and somewhat distorted sound gained widespread popularity after guitarist Dave Davies of The Kinks used a razor blade to slash his speaker cones for the band's single "You Really Got Me".

[28] Other early fuzzboxes include the Mosrite FuzzRITE and Arbiter Group Fuzz Face used by Jimi Hendrix,[29] the Electro-Harmonix Big Muff Pi used by Hendrix and Carlos Santana,[30] and the Vox Tone Bender used by Paul McCartney to play fuzz bass on "Think for Yourself" and other Beatles recordings.

[40] As clipping increases, a tone input progressively begins to resemble a square wave which has odd number harmonics.

[41] A fuzz box alters an audio signal until it is nearly a square wave and adds complex overtones by way of a frequency multiplier.

When a positive voltage is applied to the plate, a current of negatively charged electrons flows to it from the heated cathode through the grid.

The linear region falls between Multiple stages of valve gain/clipping can be "cascaded" to produce a thicker and more complex distortion sound.

[citation needed] Solid-state amplifiers incorporating transistors and/or op amps can be made to produce hard clipping.

Heavy distortion also tends to limit the player's control of dynamics (loudness and softness)—similar to the limitations imposed on a Hammond organ player (Hammond organ does not produce louder or softer sounds depending on how hard or soft the performer plays the keys; however, the performer can still control the volume with drawbars and the expression pedal).

favour this type of distortion, and thus set their amps to maximum levels in order to drive the power section hard.

This is because, technically, sag results from more current being drawn from the power supply, causing a greater voltage drop over the rectifier valve.

As this effect is more pronounced with higher input signals, the harder "attack" of a note will be compressed more heavily than the lower-voltage "decay", making the latter seem louder and thereby improving sustain.

Guitar amp modeling devices and software can reproduce various guitar-specific distortion qualities that are associated with a range of popular "stomp box" pedals and amplifiers.

Amp modeling devices typically use digital signal processing to recreate the sound of plugging into analogue pedals and overdriven valve amplifiers.

For example, a guitarist using a small amp modeling pedal could simulate the sound of plugging their electric guitar into a heavy vintage valve amplifier and a stack of 8 X 10" speaker cabinets.

In many cases, musicians playing stage pianos or synthesizers use keyboard amplifiers that are designed to reproduce the audio signal with as little distortion as possible.