(Subtle) Sidechain Compression
Even the least tech-savvy listener must surely now be aware of the sound of sidechain compression pushed to the max, given its dominance on more than a few pop (yes, I mean ‘EDM’) tracks in recent years. Of course, the technique – which we also discussed in our run through of bass production tips – has been around for decades, and can be used in a number of ways. The most extreme is the in-your-face ‘pumping’ effect, but we can also use it as a much more subtle tool for making space in the mix.
When we talk about sidechain compression we’re referring to the way in which the level detection circuitry of a compressor (originally in hardware form) can be controlled by a signal from another source (i.e. not the audio at the compressor’s main input).
If we route, say, a bassline to the main audio input of the compressor, a rhythmic element such as the kick drum can be routed to the compressor’s sidechain circuit, controlling the compression of the bass each time the kick plays. The degree and shape of this level change is determined by the attack, release, ratio and threshold controls of the compressor. Generally, a fast attack and medium-fast release are employed, though the kick drum sound itself will also affect the result.
Feeding your bassline into the compressor’s main input, with the set to alter the level by a few dBs, can enhance the groove and create a little extra space in the mix – effectively giving both parts the space they need.