In popular and electronic music, electric guitarists use delay to produce densely overlaid textures of notes with rhythms complementary to the music. 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.
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.
Doubling echo is produced by adding short-range delay to a recorded sound. Delays of thirty to fifty milliseconds are the most common; longer delay times become slapback echo. Mixing the original and delayed sounds creates an effect similar to doubletracking, or unison performance.
Slapback echo uses a longer delay time (seventy-five to 250 milliseconds), with little or no feedback. The effect is characteristic of vocals on 1950s rock-n-roll records, particularly those issued by Sun. It is also sometimes used on instruments, particularly drums and percussion. Slapback was often produced by refeeding the output signal from the playback head of a tape recorder to its record head, the physical space between heads, the speed of the tape, and the chosen volume being the main controlling factors. Analog and later digital delay machines also easily produced the effect.
Flanging, chorus and reverberation (reverb) are all delay-based sound effects. With flanging and chorus, the delay time is very short and usually modulated. With reverberation there are multiple delays and feedback so that individual echoes are blurred together, recreating the sound of an acoustic space.