Envelopes
The notion of an envelope is borrowed from sound synthesis. They are useful for modulating a value after an initial trigger, with simple means for describing the shape of a curve over time.
Anatomy of an envelope
The envelope consists of a series of stages, typically attack, decay, sustain and release.
- All stages have an associated level or amplitude. Attack’s level is also known as the initial level, and decay’s level is also known as the peak level.
- All stages except sustain have a duration, how long they run for in milliseconds.
When a trigger happens (eg. a synth key is pressed), the attack stage runs for its specified duration, after which the decay stage runs. The sustain stage runs for as long as the trigger is held. At any point when the key is released, the release stage runs.
As a stage progresses, it is essentially interpolating from its start to end point.
Envelopes can also loop through the attack, decay and release stages whilst being triggered. In this case, the sustain stage is skipped.
In ixfx, interpolation for each stage happens using a curve, allowing for more expressive progressions with the bend parameter.
You can trigger the envelope, which will then run through its stages. Use Trigger & Hold if you want to have the envelope hold at the sustain stage. Release allows a held envelope to continue on to the release stage.