When it comes to coaxing a musical sound from a track or mix, compressors are crucial tools in your signal chain.
The standard definition of a compressor is a plugin or outboard device that narrows the dynamic range of a signal. Reducing the peaks of a signal is helpful in boosting the overall level of the signal without peaking. With that principle as the foundation, there is much more that can be done with compressors.
A quick look at the way wave forms behave when amplified sheds some light onto the properties of compressors. At some point, an amplified signal begins to transform as it hits the limits of a gain stage,wherever it happens to be. For instance, a sine wave amplified to the limits of a gain stage becomes squashed against its dynamic limit, typically defined by a compressor. It eventually becomes a square wave, with harmonic distortion stacking up on top of the original waveform. To our ears, the sound becomes louder, though there is no inherent increase in volume after the limit is reached.
Compressors allow the creative engineer (YOU!) to control the parameters of this distortion by….narrowing the dynamic range of the signal, of course. This is a great way to create distortion and saturation effects without adding the overt color of distortion plugins. Distortion plugins generally have a built in tone knob, which adds incredible bias to sounds.
On the other hand, compression is often used specifically to dd color to a signal. Plugins are now sophisticated enough to emulate the sounds of vintage outboard compressors, like the Urei 1176 and Teletronix LA2A. It’snot uncommon for a producer to run a signal or track through such a compressor without adjusting the knobs, just to add the flavor of the circuitry to a signal.
If you’re just getting into compressors, it’s hard to know where to spend your cash. Start with something simple and versatile, like the izotope Alloy, Sonalksis SV-315 Mk2, or Waves Renaissance Compressor as featured in this Get That Pro Sound buying guide. What you need in a first compressor is something like this:
[The Waves Renaissance is] still my other go-to compressor for it’s solid sound and straight-forward interface. It’s relatively transparent, but does a good job of thickening synths, guitars or pretty much anything else. It’s also great for “glueing” tracks together when used on any sort of sub mix. In fact it’s actually quite difficult not to get a good sound with this plugin.
One word of caution: multi-band compressors which behave something like an EQ and a compressor, are immensely powerful tools. If you’re new to audio production, give them a pass. It’s very easy to ruin a project with multi-band compression. Until you’ve learned the fundamentals of compression, stick with normal compressors. Experience is the best way to learn how and when to use a multi-band compressor, and most engineers with sufficient knowledge prefer to not use them.