Release sets the length of time the compressor takes to return the gain reduction back to zero (no gain reduction) after crossing below the compression threshold. Very short release times can produce a very choppy or ‘jittery’ sound, especially in low frequency instruments such as a bass guitar. Very long release times can result in an over compressed sound, sometimes referred to as ‘squashing’ the sound. All ranges of release can be useful at different times however and you should experiment to become familiar with the different sound possibilities