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. Distortion is most commonly used with the electric guitar, but may be used with other instruments, such as electric bass, electric piano, synthesizer, and Hammond organ. 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. Other ways to produce distortion have been developed since the 1960s, such as distortion effect pedals. The growling tone of a distorted electric guitar is a key part of many genres, including blues and many rock music genres, notably hard rock, punk rock, hardcore punk, acid rock, grunge and heavy metal music, while the use of distorted bass has been essential in a genre of hip hop music and alternative hip hop known as "SoundCloud rap".
The effects alter the instrument sound by clipping the signal, adding sustain and harmonic and inharmonic overtones, leading to a compressed sound that is often described as "warm" and "dirty", depending on the type and intensity of distortion used. The terms distortion and overdrive are often used interchangeably; where a distinction is made, distortion is a more extreme version of the effect than overdrive. Fuzz is a particular form of extreme distortion originally created by guitarists using faulty equipment, such as a misaligned valve, which has been emulated since the 1960s by a number of "fuzzbox" effects pedals.
Distortion, overdrive, and fuzz can be produced by effects pedals, rackmounts, pre-amplifiers, power amplifiers, loudspeakers and digital amplifier modeling devices and audio software. These effects are used with electric guitars, electric basses, electronic keyboards, and more rarely, special effects with vocals. While distortion is often created intentionally as a musical effect, musicians and sound engineers sometimes take steps to [|avoid distortion], particularly when using PA systems to amplify vocals or when playing back prerecorded music.
History
Early uses of amplified distortion
The first guitar amplifiers were relatively low-fidelity, and would often produce distortion when their volume was increased beyond their design limit or if they sustained minor damage. From 1935, Western swing guitarist Bob Dunn began experimenting with a distorted or "dirty" tone. 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. 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. In early rock music, Goree Carter's "Rock Awhile" featured an over-driven electric guitar style similar to that of Chuck Berry several years later, as well as Joe Hill Louis' "Boogie in the Park".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. Electric guitarists began "doctoring" amplifiers and speakers to emulate this form of distortion.
Electric blues guitarist Willie Johnson of Howlin' Wolf′s band began deliberately increasing gain beyond its intended levels to produce "warm" distorted sounds. Guitar Slim also experimented with distorted overtones, which can be heard in his hit electric blues song "The Things That I Used to Do". Chuck Berry's 1955 classic "Maybellene" features a guitar solo with warm overtones created by his small valve amplifier. Pat Hare produced heavily distorted power chords on his electric guitar for records such as James Cotton's "Cotton Crop Blues" as well as his "I'm Gonna Murder My Baby", 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."
In 1956, guitarist Paul Burlison of the Johnny Burnette Trio deliberately dislodged a vacuum tube in his amplifier to record "The Train Kept A-Rollin" after a reviewer raved about the sound Burlison's damaged amplifier produced during a live performance. According to other sources, Burlison's amp had a partially broken loudspeaker cone. Pop-oriented producers were horrified by that eerie "two-tone" sound, quite clean on trebles but strongly distorted on basses, but Burnette insisted on releasing the sessions, arguing that "that guitar sounds like a nice horn section".
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, the recent powerful and "fat" Gibson humbucker pickups, and controlled "feedback". The resultant sound can be heard on his highly influential 1958 instrumentals, "Rumble" and "Rawhide".
1960s: fuzz, distortion, and introduction of commercial devices
In 1961, Grady Martin scored a hit with a fuzzy tone caused by a faulty preamplifier that distorted his six-string bass guitar playing on the Marty Robbins song "Don't Worry". Later that year, Martin recorded an instrumental tune under his own name, using the same faulty preamp. The song, on the Decca label, was called "The Fuzz". Martin is generally credited as the discoverer of the "fuzz effect". The recording engineer from Martin's sessions, Glenn Snoddy, partnered with fellow WSM radio engineer Revis V. Hobbs to design and build a stand-alone device that would intentionally create the fuzzy effect. The two engineers sold their circuit to Gibson, who introduced it as the Maestro FZ-1 Fuzz-Tone in 1962, one of the first commercially-successful mass-produced guitar pedals.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. Rhodes offered The Ventures a fuzzbox he had made, which they used to record "2000 Pound Bee" in 1962.
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".
In May 1965, Keith Richards used a Maestro FZ-1 Fuzz-Tone to record " Satisfaction". The song's success greatly boosted sales of the device, and all available stock sold out by the end of 1965. Other early fuzzboxes include the Rush Pepbox, the Mosrite FuzzRITE and Arbiter Group Fuzz Face used by Jimi Hendrix, the Electro-Harmonix Big Muff Pi used by Hendrix and Carlos Santana, and the Vox Tone Bender used by Paul McCartney to play fuzz bass on "Think for Yourself" and other Beatles recordings.
In 1966, Jim Marshall of the Marshall Amplification company began modifying the electronic circuitry of his amplifiers so as to achieve a "brighter, louder" sound and fuller distortion capabilities.
In the late 1960s and early 1970s, hard rock bands such as Deep Purple, Led Zeppelin and Black Sabbath forged what would eventually become the heavy metal sound through a combined use of high volumes and heavy distortion.
Theory and circuits
The word distortion refers to any modification of wave form of a signal, but in music it is used to refer to nonlinear distortion and particularly to the introduction of new frequencies by memoryless nonlinearities. In music, the different forms of linear distortion have specific names. The simplest of these is a distortion process known as "volume adjustment", which involves distorting the amplitude of a sound wave in a proportional way in order to increase or decrease the volume of the sound without affecting the tone quality. In the context of music, the most common source of distortion is clipping in amplifier circuits and is most commonly known as overdrive.Clipping is a non-linear process that produces frequencies not originally present in the audio signal. These frequencies can be harmonic, meaning they are whole number multiples of one of the signal's original frequencies, or "inharmonic" overtones, resulting from general intermodulation distortion. The same nonlinear device will produce both types of distortion, depending on the input signal. Intermodulation occurs whenever the input frequencies are not already harmonically related. For instance, playing a power chord through distortion results in intermodulation that produces new subharmonics.
"Soft clipping" gradually flattens the peaks of a signal which creates a number of higher harmonics which share a harmonic relationship with the original tone. "Hard clipping" flattens peaks abruptly, resulting in higher power in higher harmonics. As clipping increases, a tone input progressively begins to resemble a square wave which has odd number harmonics. This is generally described as sounding "harsh".
Distortion and overdrive circuits each "clip" the signal before it reaches the main amplifier as well as boost signals to levels that cause distortion to occur at the main amplifier's front end stage by exceeding the ordinary input signal amplitude, thus the amplifier.
A fuzz box alters an audio signal until it is nearly a square wave and adds complex overtones by way of a frequency multiplier.