Delay (audio effect)

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Delay is an audio effect which records an input signal to an audio storage medium, and then plays it back after a period of time^[1]. 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. It is distinct from reverb, which generally provides "reflected" sound using a different technique.

Contents 1 Early delay systems 2 Analog delay 3 Digital delay 4 Computer software 5 Uses 6 Samples 7 References

[edit] Early delay systems

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, such as Karlheinz Stockhausen, 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^[2]. 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.

[edit] Analog delay

Before the invention of audio delay technology, music employing a delayed echo had to be recorded in a naturally reverberant space, often an inconvenience for musicians and engineers. The popularity of an easy-to-implement real-time echo effect led to the production of systems offering an all-in-one effects unit that could be adjusted to produce echoes of any interval or amplitude. The presence of multiple "taps" (playback heads) made it possible to have delays at varying rhythmic intervals; this allowed musicians an additional means of expression over natural periodic echoes.

Many delay processors based on analog recording, such as the Ecco-Fonic, Maestro Echoplex or Roland Space Echo, used magnetic tape as their recording and playback medium. Electric motors guided a tape loop through a device with a variety of mechanisms allowing modification of the effect's parameters^[3]. Thin magnetic tape was not entirely suited for continuous operation, however, so the tape loop had to be replaced from time to time to maintain the audio fidelity of the processed sounds.

The Binson Echorec, another popular unit, used a rotating magnetic drum as its storage medium. This provided an advantage over tape, as the durable drums were able to last for many years with little deterioration in the audio quality^[4]. Other devices used spinning magnetic discs, not entirely unlike those used in modern hard disk drives.

Robert Fripp used two Revox reel to reel tape recorders to achieve very long delay times for solo guitar performance. He dubbed this technology "Frippertronics", and used it in a number of recordings.

Often incorporating vacuum tube-based electronics, surviving analog delay units are sought by modern musicians who wish to employ some of the timbres achievable with this technology.

Solid state delay units using analog bucket brigade delay circuits became available in the 1970s and were briefly a mainstream alternative to tape echo before being superseded by digital delays.

[edit] Digital delay

The availability of inexpensive digital signal processing electronics in the late 1970s and 1980s led to the development of the first digital delay effects. Initially, they were only available in expensive rack mounted units but eventually as costs came down they became available in the form of foot pedals. The first digital delay offered in a pedal was the BOSS DD-2 in 1984.

Digital delay systems function by sampling the input signal through an analog-to-digital converter, after which the signal is passed through a series of digital signal processors that record it into a storage buffer, and then play back the stored audio based on parameters set by the user. The delayed ("wet") output may be mixed with the unmodified ("dry") signal after, or before, it is sent to a digital-to-analog converter for output.

Many modern digital delays present an extensive array of options, including a control over the time before playback of the delayed signal. Most also allow the user to select the overall level of the processed signal in relation to the unmodified one, or the level at which the delayed signal is fed back into the buffer, to be repeated again. Some systems today allow more exotic controls, such as the ability to add an audio filter, or to play back the buffer's contents in reverse.

Digital pedals remain the most popular delay effects for electric guitarists today because of their ease of maintenance, durability, and relatively low cost. Digital delays have been criticized as sounding "unnatural" when compared to genuine echoes or analog delays, but some more recent units have made progress toward answering these concerns by adding audio filters. As digital memory has become cheaper, modern units have been able to offer rapidly increasing amounts of storage, some as large as the 16-second delay and looping machine offered by Electro-Harmonix.

[edit] Computer software

A natural development from digital delay-processing hardware was the appearance of software-based delay systems. In large part, this coincided with the popularity of both professional and consumer audio editing software. Software delays, in many cases, offer much greater flexibility than even the most recent digital hardware delays. Abundant system memory on modern personal computers offers practically limitless storage for the audio buffer, and the natural efficiency of audio delay algorithms has made the implementation trivial for delays offering shifting or random delay times, or the insertion of other audio effects during the feedback process. Many authors of software plugins have added functionality to emulate the sounds of the earlier analog units.

Software-based delays are most popular today among musicians in electronic genres or those who prefer to audition the effect in a digital audio editing and mixing environment.

[edit] Uses

The most familiar use of delay processors is by electric guitarists in popular music, notably Queen's Brian May who is cited as a pioneer of the delay effect both in the studio and during live shows[1], U2's The Edge, and Pink Floyd's David Gilmour, who frequently employ delay as a means to produce densely overlaid textures of notes in rhythms complementary to the tempo of the overall piece. Electronic musicians use delay for similar effects, and less frequently, vocalists and other instrumentalists use it to add a dense or ethereal quality to their playing. Extremely long delays of 10 seconds or more are often used to create loops of a whole musical phrase. Bill Smith, playing with the Dave Brubeck Quartet, is known for playing his clarinet through a long delay to create cascades of quick scales that repeat subtly against the sounds of the ensemble.

Echoplex is a term often applied to the use of multiple echoes which recur in approximate synchronization with a musical rhythm, so that the notes played combine and recombine in interesting ways. In fact, it was the name of a particular delay unit, the Maestro Echoplex^[5].

A "slapback echo" uses a very short delay time (seventy-five to 250 milliseconds) with little or no feedback. The effect is characteristic of vocals on 1950s rock-n-roll records, by Elvis Presley, Buddy Holly, Carl Perkins, and many others. It is also sometimes used on instruments, particularly drums and percussion, as with many of Phil Spector's works, or bass guitar, as with Tommy James's 1971 hit "Draggin' The Line". The source of this effect is a second tape recorder recording and then playing back the signal to the main tape recorder a fraction of a second later (the time it takes the second recorded tape to leave the record head and reach the same recorders playback head). This method was used on many hit recordings made for Sun Records in Memphis.

In audio reinforcement, a very short delay, often of only a few milliseconds, is used to compensate for the relatively slow passage of sound across a large venue. The unmodified signal is not played, and the delayed signal is set to leave the speakers at the same time as the sounds passing from the stage. This technique allows audio engineers to present the same signals to audience members at the back of the room at roughly the same time as they arrive from the instruments on stage, providing a listening experience with more clarity.

[edit] Samples

[edit] References

1. ^ Lehman, Scott. "Effects Explained: Delay". 1996. Retrieved on June 30, 2006.
2. ^ Gehlaar, Rolf. "Leap of Faith: A Personal Biography of Karlheinz Stockhausen's Prozession. 1998. Retrieved on July 30, 2006.
3. ^ "RE-201 Space Echo", Vintage Synth Explorer. 1997. Retrieved on July 30, 2006.
4. ^ Studholme, Richard. "History of the Binson Echorec". Retrieved on July 30, 2006.
5. ^ "Maestro Echoplex tape delay". Retrieved on July 30, 2006.