Introduction

The delay or echo adds space to the sound. Indeed, reverb and delay are basically the same things, that means sound reflections. The main difference is that the delay (or echo) produces one or several precise and distinct reflections, whereas reverb is the result of many various reflections, which cannot be heard distinctly (see this excellent article written by Vincent Burel on the subject).

In the mix, the delay often replaces the reverb because it basically creates the same effect, that would say a sound space around the main sound, but without adding superfluous sounds (as does a reverb).

Years ago, tape recorders were used to create echoes. Later, heads have been added to get more control on the repetition number and the speed. Jimmy Page, Hendrix and Ritchie Blackmore were innovators in this domain. Today, digital technology has replaced analog delays.

Settings on a delay processor are:

Type: gives a choice of several delays:

MONO-DELAY – produces one or several repetitions of the sound in MONO
STÉRÉO-DELAY - produces one or several repetitions of the sound in Stereo. Time and Feedback parameters can mostly be set independently for the left and right side.
PING-PONG – produces repetitions which are panned from one side to the other in the stereo-field.
TAP-DELAY – gives the choice of the placing, as well in the Time-space as in the stereo-field (Pan) for the repeats of sound.
SAMPLING or HOLD records a phrase you can then loop. Some machines even allow to play the sample reversed.

Time: sets the delay time. Generally, values are set in milliseconds (ms), but sometimes you can also choose other values as feet, meters, or BPM, which is very useful to set the delay on a fixed tempo.

Feedback: with this parameter you'll set the number of repeats.

Tap: by pressing the tap-button in the rhythm of the song, the delay time will automatically fit the tempo (sometimes a foot switch can be plugged to set the tempo with the foot).

MIX or LEVEL: to mix the initial sound (dry) with the delay (wet).

LOW-PASS or HIGH DAMPING (or High Cut): concerns the delay high frequency response. you use this parameter to simulate analog delays or tape-delays which were known to have difficulties to reproduce frequencies above 8kHz, adding actually warmth to the sound.

RATE and DEPTH: many delay devices have a modulation processor (chorus etc.), which colours the repeats. With the Rate and Depth parameters, you can set the speed and the intensity of the modulation.

Some examples of use

If the reverb is important to emphasize the colour of an instrument or to create a coherent sound space in a mix, it is easy to spoil a mix by adding too much reverb or by destroying the sound space with an incoherent reverb! Too much reverb tires the listening et makes the mix blurred by drowning the instruments in the diffused and omnipresent sound trail. That's why it is often replaced by the delay.

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General

A delay can be applied to all instruments (be careful with rhythmic instruments, where adding delay is very delicate). Generally, the delay is set on the tempo (Eighth, Half note, Quarter note, etc.) of the song in order to not disturb the rhythm.
If the device does not have a TAP function, or a BPM setting, you'll have to calculate these values. It is very simple if you know the song tempo (rhythm box or MIDI): you know that one minute is the same as 60.000 milliseconds and the tempo is allways given in number of Quarters per minute. you just have to divide 60.000 by the BPM to get a value for a quarter in milliseconds (ms).
Example: tempo = 120; the delay time will be 500 ms to prop up on the Quarter, and 250 ms to prop up on the Eighth (two Eighths are a Quarter). Otherwise, you will have to find the tempo with a rhythm box or a metronome. It is always better to prop up the delay (even for small values) on the song's tempo. Everything will sound more coherent. Anyway, this also applies on the modulations speed setting (phaser, flanger, etc.). Try more "exotic" values too, such as triplets for example, which sometimes gives surprising results.
Always set the number of repetitions to the strict minimum to obtain the effect you're looking for, because delays that trail in the mix, quickly become rather noisy.

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Voice

The voice nearly always needs a delay. Most of the time, it will be set in stereo spread, that means that in addition to the voice in the centre of the mix, you will add two delays to the left and the right side (for instance 20 and 30ms, or 40 and 50 ms) with a single repeat. This adds a good stereophonic image.
Another famous effect is the John Lennon like echo. It is a 120 ms delay with about 4 repeats, witch are set rather loud.
A delay setting which simulates well a reverb but without sullying or drowning the sound is a mono or stereo 200 ms delay with three or four repetitions, and which will be mixed behind the original sound.

Guitar

Guitarists are the most frequently users of delay. For a lead sound, the delay is often set on about 300 ms with three to five repeats. It can also be set on the crotchet or the half note, which is better to support the song rhythm.
A very spectacular effect is to set the delay on Sixteenths, with one single repeat, and to play a riff or a phrase in Eighths! (try the triplets too!). For a rockabilly sound, a slap-back delay style is used, with a delay-time of about 120 ms.
A rather short (20 to 60 ms) mono or stereo slap-back can also be used to emphasize a rhythm guitar. You should know that a delay of less than 20 ms is not heard as a distinct reflection, but mixed in the original sound and gives the impression of a bigger sound.
A studio trick is to pan the original sound to 8 o'clock and a 20 or 40 ms delay to 4 o'clock, which gives an impression of stereo sound.

Drums et percussions

On drums and percussions, you should use a reverb rather than a delay, because the delay desturbs too easily the rhythm. The exceptions are Reggae music and Variety (slows), where a delay is often used on the snare drum. Repeats are set on the Quarter, or most of the time on the Eighth (reggae) and feedback on three or four repeats.

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Special uses

A delay can be used to match several PA-systems in huge places (stades, open air etc.). You know that the sound covers 1080 feet per second, that means a spectator who stands at a distance of 1080 feet in front of the scene would hear the sound a second later than his friend who is just in front of the scene. This is well known, and, far away from the scene, you can see the drummer hitting the snare drum but you'll hear the sound later. If, in order to cover the whole stade, a second PA-system is set at a 1000 feet distance from the scene, the spectator who is at that place, will actually hear the sound at the same time that it is produced on the scene, but, one second later, he will hear the same sound again (coming from the first PA). Bloody mess!! If, now, you delay the sound of the second PA relative to the main system (one second in our example), things go normal and the sound becomes coherent.
You often use a small delay (some milliseconds) for the monitoring. This will really reduce feedback risks, because the sound-micro-speaker loop is cut-off by the delay.
A wide domain of use of the delay remains the modulation (flanger, chorus, phaser, etc.), because these effects are basically delays which are dynamically processed. For example, a chorus is produced by several very short delays with a delay-time changing all the time.
The flanger is also result of an echo, which was produced by a tape magneto that was speeded up and slowed down, to create this turbo-space effect. You can also approach this effect by setting the delay-time very short (2 to 6 ms) and increasing feedback. Then you play on these two parameters at the same time.

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Conclusion

Nowadays, there is are allways discussions about digital delays or analog ones. I pretend that you can do almost everything with a good digital delay unit - even simulate any analog or tape device - and these so-called advantages (warmth of the sound etc.) of analog delay units can't justify anymore the problems they create (noise, frequency reduction, tape echoes mechanical noises etc.)
Try once the Line 6 DL-4 for the guitar and even Lenny Kravitz will freak out!

References

Today, most of the digital delay units are very good, and you will have to look for for a long time to find a crappy stuff. Nevertheless, you have to distinguish small foot pedals from rack processors. The pedals are generally made for a guitar or instrumental use, and the frequency response is not the same (there is less presence/treble). Indeed, you get not as much parameters and sound quality as with a rack processor unit, but they cost only half the price. For a home studio, a pedal can be useful. For serious work, you should buy a processor (specialized in delay, or multi effects!).
Specialists such as the Line 6 DL-4 (guitar and instruments) or the excellent TC ELECTRONICS D-Two (studio) integrate many modulation effects and many settings possibilities instead of multi-effects, where the delay is just an effect among others!

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© Ziggy - Juin 2002 - English version by Seb and Espace-Cubase