What is release?
On a compressor, release is the time setting that determines how quickly Gain Reduction returns to zero after the signal falls below the threshold. It is usually shown in ms (milliseconds) or in seconds. Shorter values let go of the compression sooner, and longer values return to the original level more slowly.
Characteristics of a short release
A short release lets the compressor react again quickly to the next sound, so it tends to preserve fine dynamics and rhythmic feel. In sidechain use the level comes back fast, giving you clear pumping. On the other hand, too short a release can follow the cycle of the waveform and distort, or make the level wobble in a restless way.
Characteristics of a long release
A long release brings the gain back smoothly, which makes it easier to connect the level differences of a vocal or a whole mix naturally. However, if compression is still active when the next sound arrives, that sound stays pushed back more than it needs to be. In fast songs, check that the recovery is not spilling across the beat.
Matching it to the rhythm of the song
Watch the Gain Reduction meter and adjust how far it recovers before the next kick or phrase. It does not have to return all the way to zero; leaving a little compression for the sake of smoothness is a valid choice. Auto Release changes the time according to the incoming sound, which makes a convenient starting point when the material has large dynamics.
Careful: another parameter with the same name
The release in a synth’s ADSR is the time it takes for a note to fade away after you let go of the key. On a compressor it is the time for the compression to let go, so the meaning is different. You can hear a comparison of how the level recovers in sidechain use in How to create the ducking used in EDM (Japanese).
