We use envelopes to control how we want the sound to behave from the moment we press down on the key, to when we release the key. Envelopes can control many different parameters of the sound, some of which include amplitude (volume), pitch, and timbre.
Check out the graph below, it’s called an ADSR envelope (attack, decay, sustain, release). The X axis refers to the duration of the sound. And the Y axis could refer to any parameter that the envelope could control. Let’s say that it refers to amplitude.
The sound starts quiet, and raises to peak level before “decaying” slightly to rest at the level it will stay (sustain) until you release the key. Then, once the key is released, it will slowly become quieter until it has stopped altogether.
What sound could this envelope be in the real world? Maybe a bowed instrument such as a Violin or a Cello.
Let’s try adjusting some of these settings in Operator. With Oscillator A still selected, and still using a Sine Wave, have a look at the Operator Display again. The arrows below point to where you can toggle between an image of your Envelope and an image of your Oscillator.
While you play the keyboard, try playing with the Attack, Decay, Sustain and Release settings (measured in millaseconds). You can adjust them by clicking orange numbers below each parameter and dragging the mouse up/down, or by clicking the squares on the envelope image itself. It may seem easier to use the squares on the envelope image at first, but try using only the numerical values in the beginning. Many synthesizers don’t show a graphical representation of the envelope, so it’s helpful to understand how to use it without the image.
Try these settings:
- Attack: 20.0 ms
- Decay: 100 ms
- Sustain: -10 dB
- Release: 2.00 s
Notice how the sound’s amp envelope changed from a simple “on / off” to a slightly more complex movement.
Now try changing to:
- Attack: 2.00 s
- Sustain: 0 dB
Leave the other settings in place. The sound is much longer now as it takes a full two seconds to reach its peak and another two seconds to end after release. Long attack and release envelopes are common of pad sounds. A pad is a sustained sound typically made by a synthesizer that usually provides long chordal harmonies and background atmosphere.
Next let’s try a more percussive sound:
- Attack: 0.00 ms
- Decay: 500 ms
- Sustain: -inf dB (zero)
- Release: 2.00 s
Setting the sustain to zero means that no matter how long you hold the key down, the note will only last as long as the attack and decay time. This allows for a more percussive sound like a bell, mallet, or drum.
You’ll sometimes see envelopes with no sustain referred to as AD envelopes. These are used commonly for more percussive sounds. When you’re using a synth with an ADSR envelope such as operator to make percussive sounds with no sustain, it’s useful to set the release time to as long or longer than the decay time. This is because if the release time is set to 0.00 ms, the sound will stop immediately after you release the key, regardless of the decay setting. That being said, maybe that’s the effect you’re looking for. Try adjusting the release to hear it for yourself.