Sonic Swell
Envelope follower - generates an amplitude envelope triggered by signal level that is then multiplied by the signal to shape its amplitude. You can think of it as an AutoWah for amplitude.
Parameters:
Sensitivity
Signal level in dB required to trigger the envelope
Attack
Signal level averaging-time in seconds when the signal is coming on ("attack")
Expert Parameters:
Hold Time
Minimum envelope duration in seconds once it has begun
Release Time
Signal level averaging-time in seconds when the signal is going away ("release")