Delay (audio effect)

Delay is an audio effect and an effects unit which records an input signal to an audio storage medium, and then plays it back after a period of time. The delayed signal may either be played back multiple times, or played back into the recording again, to create the sound of a repeating, decaying echo. Delay effects range from a subtle echo effect to a pronounced blending of previous sounds with new sounds. Delay effects can be created using tape loops, an approach developed in the 1940s and 1950s; analog effects units, which were introduced in the 1970s; digital effects pedals, introduced in 1984; and audio software plugins, developed in the 2000s.

The first delay effects were achieved using tape loops improvised on reel-to-reel magnetic recording systems. By shortening or lengthening the loop of tape and adjusting the read and write heads, the nature of the delayed echo could be controlled. This technique was most common among early composers of Musique concrète (Pierre Schaeffer), and composers such as , who had sometimes devised elaborate systems involving long tapes and multiple recorders and playback systems, collectively processing the input of a live performer or ensemble.Audio engineers working in popular music quickly adapted similar techniques, to augment their use of plate reverb and other studio technologies designed to simulate natural echo. In the late 1940s and early 1950s, several sound engineers began making devices for use in recording studios and later more compact machines for live purposes. Guitarist and instrument designer Les Paul was an early pioneer in delay devices. A landmark device was the EchoSonic made by American Ray Butts. It is a portable guitar amplifier with a built-in tape echo, which became used widely in country music (Chet Atkins) and especially in rock and roll (Scotty Moore).

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