Perhaps the most famous of these sounds—or, at least, the most formative—is that of Dave Davies, the lead guitarist for The Kinks, who got bored of his Elpico amplifier in 1964 and decided to pierce its speaker cone with a razor blade. This effect, known as “clipping,” cuts off the audible waveform at the height of the amplifier’s limits (voltage, current, and thermal), thereby distorting the signal. Although Link Wray had been doing this since the late 1950s, Davies popularized guitar distortion in the first few moments of “You Really Got Me,” changing guitar music.

Artists have been converging on this sound for more than a decade before Davies used it. In 1951, “Rocket 88” by Ike Turner and the Kings of Rhythm took advantage of a distorted amplifier that had been damaged in transport. The same thing happened to the Johnny Burnette Trio in 1956, when Paul Burlison pulled out a vacuum tube from his amplifier after it fell off the top of the band’s car. He loved the sound so much he used it to record “The Train Kept a-rollin,” which inspired a whole raft of British musicians:

Most lo-fi amplifiers in the 40s and 50s produced unexpected distortion or overdrive tones at higher volumes. Guitarists quickly discovered that the Fender Tweed Champ (originally marketed to beginners as the Champion 800 in 1948) produced a distorted sound at high-volume levels thanks to the Champ’s low power output and simple circuitry. Many of the classic guitar solos in the 1950s were recorded through a Champ, which resembled a wide-panel TV cabinet covered in tweed cloth. Leo Fender even went so far as to manufacture the first 100-watt amplifiers for surf guitar pioneer Dick Dale, who had blown hundreds of Fender amps and speakers from regularly turning up the volume.

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The history of signal modification isn’t just one of pleasing the ear through unconventional methods. It works both ways: Guitar effects have modified their users, just as much as their users and engineers have modified their sound. New effects can change a guitarist’s playing ability completely, concealing their technique as well as embellishing it. U2’s The Edge, for example, is known for his restraint of technique by embedding different rhythms within delay settings.

Some effects, and the boxes that produced them, altered musical periods beyond recognition. The valve-driven Watkins Copicat, for example, will forever be associated with the sound of the late 1950s British music “beat” scene. Developed by Charlie Watkins in 1958, this odd machine supported a tape-recording mechanism that would record and play back any sound with varying lengths of delay in-between the replay heads. The device was critical to the rockabilly sound of the late 1950s, the “beat-group” sound of The Shadows, and the Liverpool Merseybeat scene of early 1960s (as well as the Birminghambeat, or Brumbeat scene). The sensation of hearing a guitar warble and wail to its own output encouraged guitarists to experiment with different styles of attack and vigor. For example, the noise that begins and ends the original 1962 recording of “Telstar” by the Tornados was made using the Copicat by creating a loop of echo and reverb effects. This produced what can best be described as some sort of space-echo/attack-helicopter noise.

Some effects produced dramatically weird sounds that were largely impossible to pull off. The peculiar 1948 DeArmond Trem-Trol (used extensively by rock-and-roll pioneer Bo Diddley) altered the volume of the guitar signal by exposing the connecting pin to a brass-and-glass canister half-filled with shaking, water-based electrolytic “Hydro-fluid.” The shaking—and often leaky—fluid washed over the pin and would bend the signal’s volume, causing an oscillating, watery tone. In the words of Chris Gray, one of its few remaining owners, “This is not a subtle effect—it adds all its personality to your sound whether you’re ready for it or not.”