Compression is the second most popular effect processing of audio, behind equalisation (eq). Near enough every engineer will use it on a daily basis and it forms one of the core pieces of kit in both on-board and outboard collections. The compressor is generally used to control the dynamics of an inputted source, by taming any larger peaks by an amount set by the user. The more ferocious the compressor is set up, the more it will change the sound of what is going through it. As with any processing tools, one can really abuse its parameters and use it as an effect to gain a different end result.
A great abuse of a compressor is a technique called parallel or New York compression. The most popular, and least time consuming, way of achieving this is to send a (or group of) non or partially compressed signal(s) through an auxiliary channel containing a compressor and run this alongside the original source sound, mixing to taste. Other ways of achieving the same results, are to copy all of the tracks you wish to use parallel compression on, applying the particular compressor and settings to each, and, as before, mixing them in to taste with the original sound(s). Why would you want to do this in the first place? In short, parallel compression increases the presence in a mix, as well as fattening up whatever it is you are parallel compressing. This is done whilst maintaining the dynamics of whatever it is you are affecting. The technique can be used on any instrument: drums, bass, distorted and acoustic guitars, piano, vocals and so on. The most widely used application is on drum kits, as it adds a nice fat bottom end to a kick and snare, whilst simultaneously making them sound bigger and cut through the mix. As with anything in sound engineering, there are no set rules on how to go about it, but it is rare an engineer will parallel compress a whole kit, favouring the kick and snare and sometimes the overheads and toms, which, when parallel compressed at differing amounts, can produce a slightly different effect, as explained below. Another great use is to “trash up” a drum kit, this works most effectively with rock and indie kits as it adds a little more aggression and punch to the kit. The best way to achieve this is to parallel compress the tom, overhead and room microphones. Again, this is subject to what works for you and which you find most effective. When setting up the compressor for this type of compression, a high ratio, maybe as high as 14:1, if not higher, a fast attack, hard knee and fast release are a good place to start. Then it is a case of tweaking until satisfied. You’re looking to hear the compressor working hard as an effect as opposed to a subtle, or not so subtle, taming of dynamics. The initial attack of the toms and cymbals will have a more explosive quality to them, whilst not affecting the decay and the kit gains a grittier edge with the pumping of the compressor.