How do delay lines create so many effects?

Question

I was trialing this audio plug-in from SonicCharge (there's a program demo in the site).

It claims to be based on a delay line and uses some logic to modify it:

At its core is a 12-bit digital delay with variable sample rate from $0$ to $352\textrm{ kHz}$. The delay is controlled by a programmable processor that allows you to change and modulate the delay time with various "operators".

I know from previous readings that delay lines can be used to construct a pitch shifter.

What are the properties in the delay line that allow for such numerous applications?
I.e. what is it based on that the delay line can create such a varied amount of effects?

Answer 1

A DSP / Audio delay line doesnt create any effect in itself, a delay is simply a timed delay in the signal. it has no sound difference, it repeats the sound once and mixes it over original or sends it to a different mix line.

A feedback delay repeats the sound multiple times at the delay interval frequency, it sounds like a digital echo, and can become an oscillator above 20hz. almost all fx delays use variable feedback controls to control the number of repetitions of a sound, and they are filtered out as they feed back therefore diminishing.

Modern delays can work like grain synth samplers and often are based on them which have integrated effects like pitch shifting and research Grain-Delay and Grain-Resampling for infor about that. Squarepusher is somneone who uses alot of grain delay sometimes...

So a delay in effect is barealy an effect, but it can become an osciallator, has complex variants, and can feed into other lines that have any kind of additional FX.

To get a firmer grasp of that program i foudn this vid was more informative:

https://www.youtube.com/watch?v=ySzjFU6J4Ck

it's a pretty simple and very well balanced grain-delay with good controls and some bit crushing types of FX, and probably some filters too.

Answer 2

As far as I know delay is like the holy grail of effects processing. First off delay lines can be used to create filters. If we delay a sound by one sample and play it over itself we can make the simplest LP filter. By extension, EQs are made of delay lines, since these are just a number of filters combined. Slap back delays are also, naturally, made of several delay lines, with more time in between than filters which are too close for our ears to perceive as two distinct sounds. Chorus and flangers are also made by delays but here the delay time is modulated.

I hope this gives you some insight into the power of delay!

Answer 3

"Delay Effect" refers to more than just a simple delay. Typically there is a feedback parameter that allows running the output back into the input so multiple echos are created. This feedback path often has a filter that allows shaping the frequency content of the echos.

Fancier delays have multiple "taps" that can be combined or fed back to create specific temporal patterns.

When the delay amount varies with time, the frequencies of input signal will indeed be changed. However, that's not a actually pitch shifter (which changes frequency while maintaining the signal timing) but it's more a modulation effect like a Chorus, phaser, of flanger.