Attack, Decay, Sustain, Release : ADSR Explained

ADSR

Attack, Decay, Sustain, Release : ADSR Explained

 

Since many of my followers play electronic keyboards, today I’d like to explain what ADSR Envelope means.

The ADSR Envelope is a key element used to shape the sounds used on samplers and synthesizers, ADSR is the abbreviation of Attack, Decay, Sustain and Release.

These 4 terms are associated to values used to modify the sound in its duration and can be applied to several targets, the most common targets are volume, pitch and filter.

For example, if we have an ADSR envelope applied to the volume level then the Attack value will determine how fast a sound reaches it’s maximum volume, the Decay will determine how long it takes to drop down to the sustained level, the Sustain will determine what level of volume the sound will remain at while the sample or synth remains triggered (key is held down), and finally the Release will determine how long it takes the sound to fade out from the sustain level after the key is released.

If you combine ADSR envelopes, not only on volume, but also on filters and/or the pitch you can imagine how power is this system to shape your sounds.

Most modern synthesizers also allow you to set the duration and the target value for each sounds phase (Attack, Decay, Sustain, Release).

One of the most important features of this system is that you can easily emulate the “timbre” of other instruments or to build brand new instruments using the same sample as a base but appling several ADSR envelopes to several targets.

Here is a detailed description of each “phase”, as said in many modern synths you can also define the target value of each phase but here, to make the article more readable, I’ll describe only the duration parameter of each phase:

Attack

Attack is the duration or time that it takes for a signal to reach the highest point of amplitude after being triggered. Often the attack of a sound is so quick that it is perceived as happening instantly, and then quickly followed up by the decay phase of the ADSR envelope, although it’s common to have a longer attack phase on certain synthesized sounds (like pads for example).

Decay

Decay, like attack,  is a parameter that sets a duration – But rather than the time it takes to increase the volume level, decay represents the time it takes to drop down to the sustain level after reaching the initial peak of the attack phase.

Sustain

Sustain is the only factor in ADSR that doesn’t represent time. The sustain is a level of amplitude that the signal remains on for as long as the sample/synth/sound is being triggered. In regards to a keyboard, the duration of the sustain is determined by how long you hold down a key.

Release

Release, as with attack and decay, represents a change over time. The release phase begins as soon as the sample stops being triggered (for example when you stop holding the keyboard’s key down).

The release parameter determines how long it takes for the sound to fade out completely from the sustain level. You can think of it as the opposite of the attack in a sense.

Conclusions

ADSR Envelope is a very important concept you should master if you want to create sounds or change your synth’s internal sounds, as I said, it’s used mainly to shape the volume level but on modern synths and keyboards you can apply an ADSR curve also on filters, pitch, effects and many other parameters.

Of course you can find ADSR Envelopes also on DAW, VST Instruments and on almost any hardware/fostware that can electronically emit a sound.

If you have questions post them on the comments!

 

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2 Replies to “Attack, Decay, Sustain, Release : ADSR Explained

    1. Hi ALex, you are right it could be more clear but as stated from the article :

      Sustain is the only factor in ADSR that doesn’t represent time. The sustain is a level of amplitude that the signal remains on for as long as the sample/synth/sound is being triggered. In regards to a keyboard, the duration of the sustain is determined by how long you hold down a key.

      Time is partially involved because : the duration of the sustain is determined by how long you hold down a key

      I’ll try to explain more clearly, thank you for the feedback 🙂

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