F (Filter) envelope copes with the opening/closing of the filter. Let’s play with this one later.
A (Amplitude) envelope copes with the amplitude, or amplification of the sound in itself. It carves in time the sound. As such, this is the most important parameter to try and mimic this or that instrument.
Let’s go through ADSR (Attack, Decay, Sustain, Release)
Attack is the TIME the note takes to go from no sound to maximum volume when you hit a key.
Decay is the TIME the note takes to go from maximum volume to sustained volume.
Sustain is the VOLUME at which the note is kept as long as you hold the key.
Release is the TIME the note takes from sustain volume to no sound when you release the key.
Some combinations aren’t very impressive: A to 0, D to 0, S to 0, R to 0: no sound or a very very very short tick.
Let’s put Sustain to the max ok? That’s it, full simple gate, hit a key = sound, hold a key = sound, release the key = silence.
Now that’s quite harsh, surely if you try to approximate some real instrument (strings, organ, flute, whatever).
Maybe add some attack time, some release time at first. That’s smoother already. Pads are somewhere there.
Now, some sounds need percussive characteristics, try and add short decay and lower a bit sustain. Now the note begins by a kind of volume burst, then stabilize at a lower cruise level.
Some sounds simply need to decay in time, whatever you hold with the keys. That’s with sustain level at zero and release at some value long enough to hear the decaying note.
But to hear a note, all the three other TIME parameters need to cumulate in an audible note that takes some time to disappear.
Well, if you can imagine the curve all these params draw in time (simple two axis diagram, in Y, volume, in X, time),
you can also imagine using such a curve to drive the opening/closing of the filter. This helps the carving of the sound, by letting you colour (darken, lighten) the note during its time presence. A bit abstract at first, but you’ll get to it playing with the settings.
Filter cutoff knob and sustain knob define both the min and max, EG AMT in the Filter section defines the amount of influence the Filter envelope has, and also the sense of its influence (positively or negatively). These two supplementary steps add some difficulty to grasp simply the filter envelope, at least for me.
When you manipulate the Filter envelope, maybe first use an Amplitude envelope of the simplest type, A = 0, D = 0, S = full, R = 1 or 2 secs, so you hear the change you do.
All the best,
Greg