Compression is one of the most common things you will find in a studio, right up there with mics, amps and computers. Compressors are often built into preamps, but more and more often they are used as plug-ins after recording has taken place. You’ll likely see compression on individual tracks, in bussed groups of tracks, on overall mixes and in mastering sessions. In basic terms, compression pushes down dynamic levels so that the overall level can increase without clipping (the distorted sound that occurs when a signal is too loud). In other words, the very loudest part of a track is made quieter so that the entire track can be louder. But how much compression is too much?
Too much compression can suffocate a track’s sound. While you want your song to be as close to radio-level as possible, over-compressing will only ‘squish’ your sound, making it sound unnatural and dull. Use your ears to determine how much compression a track needs. An acoustic guitar track for a folk song, which would need to sound natural and dynamically rich, will obviously use less compression than a speed metal rhythm guitar, which needs only to be as loud and tight as possible.
Use compression in master tracks to ‘glue’ your individual tracks together. Striking a middle ground among your song’s dynamic levels is crucial to making the song sound cohesive; this is where compression comes in. There’s a galaxy of compressor plug-ins out there, and like anything else, experimentation, an open mind and a trained ear will make all the difference in creating a successful song.