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 tape recording, such as Ray Butts' Echosonic (1952), Mike Battle's Echoplex (1959), or the Roland Space Echo (1973), 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.In the case of the popular Echoplex EP-2, the play head was fixed, while a combination record and erase head was mounted on a slide, thus the delay time of the echo was adjusted by changing the distance between the record and play heads. In the Space Echo, all of the heads are fixed, but the speed of the tape could be adjusted, changing the delay time. 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.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. John Martyn is widely acclaimed as the pioneer of the echoplex. Perhaps the earliest indication of his use can be heard on the songs Would You Believe Me and The Ocean on the album Stormbringer released in February 1970. This was a first taste of things to come from Martyn’s interest in electronics and the boundless possibilities of electric music. Glistening Glyndebourne on the album Bless The Weather (1971) showcased his developing technique of playing acoustic guitar through the echoplex to stunning effect. He later went on to experiment with a fuzz box, a volume/wah wah pedal and the echoplex on highly acclaimed Inside Out (1973) and One World (1977). Martyn is cited as an inspiration by many musicians including U2's The Edge.
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. Though solid state analog delays are less flexible than digital delays and generally have shorter delay times, several classic models such as the discontinued Boss DM-2 are still sought after for their "warmer", more natural echo quality. Additionally, several companies make new analog delays, including the MXR Carbon Copy and Ibanez AD9, a reissue of their 1980s-era pedal of the same name. Behringer makes a "clone" of the Boss DM-3, called the VD400, and BBE makes a derivative of the Boss DM-2, called the Two Timer.
Old delay systems like the Roland Space Echo and Echoplex are still highly regarded and used with some frequency by modern bands. The Space Echo has been recreated as a digital emulation by the Boss Corporation with the RE-20 Space Echo pedal.