So how does a compressor actually work? I’m going to start out by talking about a conventional four-control compressor, which is pretty much the norm. The four standard controls are THRESHOLD, RATIO, ATTACK, and RELEASE, or occasion- ally variants thereof. Makeup gain, included on virtually all compressors, is just a simple gain (volume) control that comes after the compressor and that is completely independent of the action of the compressor. I will also refer to things like “circuits,” pretending that we are still in the analog realm, but the principles apply to plugins as well.
How Audio Compression Works