Bus compression 101

Let’s look at the art of compressing your entire stereo mix, also known as ‘two-bus compression’. Compressing your whole track in one go can add punch to drums, and density to everything, but probably the most famous use is to ‘glue’ a mix together, and make it sound ‘like a record’.

When a compressor is squashing the whole mix together, every loud drum hit will duck the rest of the parts momentarily, causing the elements to bounce along in time and groove a little better. With typical low-ratio, low-threshold settings, the compressor will be riding the signal most of the time, so everything will start to subtly affect everything else, and all the elements will be shaped around one another, to create that sought-after unified ‘whole’.

But mix bus compression doesn’t always work as a magic ‘make-it-better’ trick. Sometimes, you’ll find the process just dulls or constricts the sound, no matter which compressor you choose. This can be a particular issue if you’ve left the compression to the later stages of your mix, as you already have a balance that you’re happy with, and compression will inevitably change that balance to some degree

If you’re in this position, don’t worry. You don’t have to start the mix all over again. There are many other ways to introduce a similar kind of interaction between different parts of your mix. Perhaps the most fashionable of these is parallel compression, whereby you smash dynamics and then mix this signal side-by-side with the uncompressed stuff you started with (via either a send/return setup or with the compressor’s dry/wet mix knob). Although this is generally used on one single element (say, a snare), or a group of related instruments (ie, your drum bus), things get arguably more interesting if you send your vocal to the same parallel compression bus as, say, the backing vocals, guitars and keys. This will result in complex interactions between those elements, which can then be tucked subtly under the rest of the mix to add life and energy. This is the kind of thing Andrew Scheps likes to do with his famous ‘rear bus’ technique – Google is your friend if you’re unfamiliar.

Then there’s sidechain compression, most famously the ‘kick-ducks-bass’ or ‘kick-duckspad’ trick used in electronic music. The same approach can be used for other elements of the mix as well. Let’s dive in and look at a few ideas…

“There are many ways to introduce interaction between parts”