: Decay vs Sustain on synths Could you explain to me the difference between "decay" and "sustain" on synths? I'm using the Korg Kronos 2 and the synth engines have both sustain and decay and they seem to be doing the same thing

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The ADSR envelope (and derivatives) is as follows:

A: Attack - the length of increase in voltage* (or analogue)

D: Decay - the length of decrease in voltage that comes after the increase

S: Sustain - the amount (or level) of voltage to sustain after the decrease

R: Release - the length of time it takes for the voltage to go back to 0.

Telling the difference between Decay and Sustain when using a volume envelope can be difficult as you will only be hearing the difference in loudness. I recommend, for experimentation purposes, using (or routing) the envelope on the low-pass filter. You will hear differences more clearly when you are listening to changes in timbre. You will then be able to play with the decay which will cause the sound to be plucky (that's my word and I'm going to stick with it) while playing with the sustain will cut short the pluckiness but have a steady sound come after you play a long note.

A high decay value means that pluckiness is drawn long. A low decay value means that it is going to be short. A high sustain means that the decay will not sweep through the whole range but get stuck at a higher timbre. A low sustain value means that the decay will sweep more until it stops.

This can be applied to other parameters as the synthesiser permits.

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Kronos Synth has some advanced ADSR modeling features to tailor your sound.

Click here for the Kronos manual.

EGs (Envelope Generators)

The modeling section is divided into three parts: Level, Time, and Curve. All of these three components are defining a single curve, so when adjusting your sound, it is important that you check all three of them.

Also, due to these advanced options, it is possible to create an inverted ADSR curve shape, that is, an upside-down ADSR curve shape.

Level (In order of sequence):

Start (0): Initial level at time 0
Attack (A): Level to change to following the start level
Break (B): Level to change to just before the sustain level
Sustain (S): Level to sustain before the key is released

Time:

Attack: The length of time between the start level and the attack level. t(0)~t(A)
Decay: The length of time between the attack level and the break level. t(A)~t(B)
Slope: The length of time between the break level and the beginning of the sustain level t(B)~t(S)
Release: The length of time between the end of sustain level and the release falloff t(S)~End

Note: Take note that sustain time is not included as it is dependent on how long you hold the key. The length of sustain ends upon release of the key.

Curve:

I can't find detailed information on the curvatures available, but it appears that 0 is a linear curve and I am guessing that it gradually accentuates the S curve as the numbers get higher.

Attack, Decay, Slope, Release

Final Note: In Kronos, the levels and times are defined by values 00 ~ 99, which most likely are percentages of some given voltage and a time frame (ms).