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Envelope generator

The envelope generator (EG) generates an ADSR envelope. The envelope being the way in which the level changes with time and is controlled by the Attack, Decay, Sustain and Release parameters. Its function is to modulate some aspect of the instrument's sound (often its loudness) over time.

FabFilter Twin 2 - Envelope generator

Since you need at least one EG to make a sound, you cannot delete the first EG, called Main EG. The Main EG differs from the other EGs because it doesn't have trigger, threshold and delay parameters and always has a range from 0 to 1. The Main EG also has a component button counterpart in the top synth section of the interface, enabling you to tweak attack, decay, sustain and release directly without having to open the modulation section.

Main EG Component Button

To add an envelope generator as a modulation source, click the + button in the source selection bar and click New Envelope Generator.

The following EG parameters are available:

  • Trigger
    The EG can be triggered by two different kinds of input: MIDI note events (MIDI) or the signal from the side-chain (Side Chain). When MIDI is selected, the Threshold knob is hidden. Depending on the type and amplitude of the incoming side chain signal you need to adjust the threshold for optimal functioning. Look at the top segment of the source button for the EG to see when it is in the triggered (Attack-Decay-Sustain) state. See also Using the side chain.

  • Delay
    The time it takes for the attack to start after the key is pressed (or triggered when the side-chain signal exceeds the threshold).

  • Attack
    The Attack portion of the envelope is the time taken for the amplitude to reach maximum value. Slow attack is commonly part of sounds called pads. But for percussive sounds the attack time should be as short as possible.

  • Decay
    After the sound has reached its maximum level, it starts to decay until it reaches a level known as the Sustain level at a rate set by the Decay time setting.

  • Sustain
    This is the level reached after the decay time. The EG will hold this level as long as a key is pressed. Note that this parameter specifies a volume level rather than a time period.

  • Hold
    Once the key is released, the value will remain at the sustain level for a time set by the hold parameter.

  • Release
    After the hold time the sound resumes its decay, this time at a new rate determined by the Release setting.

  • Range
    Normally, the EG works with a range from 0 to 1 (the top option), but you can also choose to change the range so EG outputs 0 at the sustain level. It will attack from a negative value to a positive value, and finally release to a negative value. The EG "centers" around the 0 value, which can be useful for modulation.


  • When adjusting the EG control points, you can hold down the Shift key to fine-tune a setting, just like with regular knobs.
  • To let a sustain pedal control the EG, you can hook it up to the Hold setting. The recommended way to do this is via a MIDI source.

At the top right of the EG interface, the Presets button provides access to the EG section presets. The Remove button deletes the envelope generator. You can customize the default EG settings (used when creating a new EG) by overwriting the predefined Default section preset.

Next: Envelope follower

See Also
Drag-and-drop modulation slots

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