I thought the same when I started out. These are valid questions to ask.
Understanding these terms will help you shape your sounds into amazing synths and instruments.
Let’s break it down:
A = Attack
D = Decay
S = Sustain
R = Release
Attack is the very start of the sound, usually from silence to full volume.
Decay starts at the peak of the attack and drops in volume until it reaches the Sustain point.
Sustain is the steady volume of the sound once the attack and decay cycle is complete. Sustain doesn’t have a preset length, it as a constant until the note is no longer played.
Release is the decrease of volume from the Sustain point until it reaches zero.
There are always exceptions to these definitions, but these are standards and very common formats for the shape of a typical sound or instrument.
Now let’s take a look at an Envelope.
The Envelope is the collection of the ADSR, the shape of the sound or instrument, as seen below.
The attack in this example is the first orange dot along the red line leading to the second orange dot. This is the volume of the sound going from zero to max.
The decay is the second orange dot leading to the third. This is a decrease in volume.
The third dot is special. This represents the Sustain and is constant, having no associated line to travel.
When the Sustain is over, the third dot leads to the fourth which is the Release. This is the journey of the sound’s volume back to zero.
Now you have a basic understanding of the Envelope and it’s ADSR components. Time to open up your DAW and start messing around with your favorite synth.
Until next time, good luck and keep making music.