06/12/2025
After a compressor attacks a transient, it has to release it. Just like the attack time is variable-altering the slope of the transient-so is the release time; it’s just the time it takes for the compressor to turn off the gain reduction, letting the signal recover. Think of it like a light switch, or the gas pedal in a car. How quickly does the light turn on? How quickly does your vehicle accelerate? And how quickly are you back to the initial state?
As seen in the first chart, it’s not necessarily a linear process, depending on threshold, ratio, and other characteristics inherent to the compressor. It isn’t always the speed at which the signal reaches its original level. It’s just how quickly the compressor releases the transient. For example, with a 150 ms release time, a deeply compressed signal may still take longer to fully recover, and this is dependent on the attack time as well. Using long release times can actually soften the attack of the transient, resulting in a more evenly compressed signal. As with every tool in audio, this is useful in some applications (like increasing or enhancing sustain) and very much unwanted in others (certain program material).
In the final images, we see captures of a short bit of audio, where the attack time remains the same, but the release times are changed. The overall level gets lower and less dynamic with longer release times in this case, since the transients are happening while the compressor is still in recovery. As evidenced in the last shot, a slow release time on program material can be problematic with too deep a threshold, too large a ratio, and/or too fast an attack time.
Notice how the signal is initially louder on the left, then gradually slopes downward to a flatter, more even level. The sound is very recognizable: you’ll hear the snap of the first transient, then the compressor struggling to recover after the initial loudness, pumping through the rest of the material. This sound can get buried, to an extent, if followed by an aggressive limiter, but that’s one of many ways it’s easily missed.