Envelopes
Hold a real piano key: the sound leaps out, then fades while you hold. A violin swells in slowly. A struck bell rings long after you let go. None of these are about pitch or timbre, they're about how loudness moves through time. In a synth, that motion is drawn by the envelope.
The classic envelope has four stages, ADSR:
- Attack: time to reach full volume after you press the key.
- Decay: time to fall from the peak to the sustain level.
- Sustain: the level held for as long as the key stays down (a level, not a time!).
- Release: time to fade to silence after you let go.
This is the moment synthesis starts sounding like an instrument. Play the keyboard and reshape the envelope, the glowing graph shows exactly what your four knobs are drawing.
Try this: the three presets are three instrument families. Pluck: instant attack, no sustain, guitars, keys, drums. Pad: slow attack, long release, strings, atmospheres. Organ: on/off like a switch. Most sounds you'll ever design start as one of these three gestures.
Checkpoint
Play both notes. Which one has the slow attack?
Checkpoint
Sustain is different from the other three ADSR stages because…