Simple linear envelope generator.
| gate |
This triggers the envelope and holds it open while > 0. If gate < 0, force release with time |
| attackTime |
The duration of the attack portion. |
| susLevel |
The level of the sustain portion. |
| releaseTime |
The duration of the release portion. |
| doneAction |
An integer representing an action to be executed when the envelope is finished. See Done for more detail. |