Production Techniques: ‘Delay and Echo’

History

We have all no doubt experienced the phenomenon knows as echo; yelling from the top of a cliff or canyon and then hearing our voice bounce back after time? Delay works off similar principles, however is created artificially in the studio environment. The history of delay hearkens back to the 1950’s and was created by using analogue tape machines. This tape delay became part of the iconic sound of Elvis Presley, Buddy Holly and Les Paul. Tape delay used the design of the machine with its ‘record head’ (first in line) and ‘playback head’ (after record head), to good effect and it worked like this: The signal would be recorded from the mixer (printed to the tape), and whilst the tape was still rolling, this recorded signal would then travel to the playback head. You will note that as per the diagram below there is a distance between the two heads, so this signal transfer took time to arrive at its destination. The design of the machine and gap between heads determined how much time. This delay was also influenced by the tape speed.The last stage in the process was to play the signal back from the playback head to the mixer, resulting in the tape delay. This effect was known as ‘slapback echo‘ and was used extensively in Rockabilly and pop music in the 50’s and 60’s to create a richer, warmer and fuller sound which could make your trio sound like a band with double the

members. Soon enough, dedicated ‘echo boxes’ were invented including the Echoplex (1961) and the ‘Roland Space Echo‘ (1974). These units were quite expensive and bulky (rack mounted), but as with all technology, soon became smaller, cheaper and eventually with the arrival of the digital revolution, made available as foot pedals (mid 80’s)>>>

Delay Today

The principals of delay have remained the same. Take a signal, hold onto it for a predetermined time and then play it back (often more than once). Our modern software plug ins work similar to a sampler in that they record, digitise and store this signal in an audio buffer. They then replay the sampled audio back at the user defined time after the original signal has been heard. Most hardware delay effects units and DAW plug ins have five key settings that allow the operator to adjust what the delay will sound like:

Delay Time: the amount of delay (always set in milliseconds), determines how long it takes for the stored signal to reappear in the mix.
Feedback / Regeneration: This setting is used to actually send the signal back into the mix and the amount of times the signal is sent back and delayed yet again, is up to the programmer.
Low Pass Filter: Ridding the signal of the higher frequencies can be useful in creating a feeling of distance and sending the delayed signal back in the mix. This filter can also help de-clutter the mix and have the listener hearing the key elements you want emphasised at that point of the song.
Polarity Reverse Switch: This setting allows the user to reverse the polarity which may seem counter-intuitive, but can really help at times when using delay (which can have a tonal impact on the frequency spectrum), particularly with comb filtering and flanging (more on this later).
Input/Output Level: When passing through the delay we do not usually want gain changes, so this setting is used to control this element.

Types of Delay

Long Delay: This delay is usually associated with Echos and the delay times are greater than 50 – 60 milliseconds. Above this range (depending on the signal), is where you can clearly hear a second or separate repetition of the original sound.

Medium Delay: Creates Chorus, Thickening and Doubling effects with delay times of 20 – 50 milliseconds. In this region we still perceive the delay, but our mind does not acknowledge a repetition of the original sound event, the two begin to fuse together.

Short Delay: Generates Comb filtering and Flanging effects with delay times of less than 20 milliseconds. Now we are hearing one sound but it is a different one tonally and texturally than if the original was played with no delayed signal added.

Conclusion

The modern software used to create delay effects has much more flexibility than the previous analogue and digital effects units. Software delays can be much longer in duration and are cleaner and crisper than the warmer and grittier analogue delay units. The technology is now so advanced however and has had so much attention paid to the algorithms necessary, that we can still achieve closer to the analogue sound using software than ever before. Stereo delays are now also possible which can create a richer stereo field by using ‘Ping Pong Delay‘.

The new delay plug ins also allow the engineer to apply countless additional audio effects like modulation and filters to the delayed signal. This effectively grants them the new privilege of generating limitless variations on the original sound source and creating new and interesting textures for our evolving ears to enjoy.