It’s a common piece of (good) advice that you should allow each instrument in your mix its own space. When instruments start to encroach on each other’s territory it can quickly lead to a cluttered and muddy-sounding mix. Usually we use EQ to counteract this – for example, perhaps carving out some of the lower-mid frequencies on the kick to allow space for the bass. One other possible technique, however, is to use a compressor with a side-chain in order to allow competing instruments to coexist happily. What we do here is to apply a compressor to one track, but allow the other track to act as a trigger. The result is that when the second track is not playing (or is only playing quietly) the first track plays as normal, but when the second track kicks in, the first track is reduced in volume by the compressor. This technique is called side-chaining, or 'ducking'.
Once again I’ll be using Cubase 4 as an example. There are several ways to achieve side-chaining in Cubase, none of which are quite as quick and intuitive as they probably should be. The specifications for VST3 include side-chaining natively, so hopefully in the future it will be a bit simpler.
Here I’ll demonstrate one way of creating the familiar ducking bass effect that you’ve probably heard on many dance tracks. For the method I’m going to describe here you will need a VST compressor that features a side-chain input. Here I’m using the Sonalksis SV-315 mk2, an extremely versatile compressor with side-chaining ability. If you want to try this tutorial out, a 30-day fully-working demo of this compressor is available from sonalksis.com.
Here’s how you might set it up in Cubase 4:
Create a ‘Quadro’ group channel. Go to Project -> Add Track -> Group Channel -> and under Configuration, select More -> Quadro. In your Group channels you’ll now see your newly created group. For the sake of clarity, rename it ‘Sidechain’.
What we’ve done here is to create a group channel with 4 inputs. We do this because the first two inputs will be used to receive the signal from the kick as a trigger for the compressor. Inputs 3 and 4 will then be used for the bass, which we want to be affected by the kick.
On the kick drum channel, click on an empty ‘send’ effect space, and then select Groups -> Sidechain. Increase the volume on the send to 0.00, and click the ‘Pre’ button; we select ‘Pre’ so that we can change the volume of the actual kick in our mix later on if we like without changing the ducking effect that we are about to set up.
Now go to your Sidechain Group channel. On the Inserts, insert your compressor with sidechain ability. In this example we’re using Sonalksis SV-315 mk2. Click the ‘Ext’ switch in the side-chain area of the Sonalksis compressor.
Play the track in a place in which both the kick and bass are playing at the same time. In the Sonalksis compressor, lower the threshold until you see the gain reduction meter moving with the beat of the kick. Listen to how the bass is ducking out of the way every time the kick is hit. The further that red bar moves to the left on each beat of the kick is the amount that the bass is being ducked.
Using just a little bit of this effect will give your kick and bass tracks a little more cohesion. Adjust the threshold and ratio of the compressor until you hear the amount of ducking that you want – how pronounced you want the effect to be is entirely up to you!