If you’re into electronic music production, you’ve probably heard the term “sidechain compression” more than once. For those unfamiliar, sidechain compression means using the output of a track, such as a kick drum, to trigger the compression on another track, such as a bassline.

Assume you’re watching a movie and there’s a scene with no dialogue or sound effects. Here, the soundtrack can be blasting. However, as soon as dialogue comes back, the music needs to duck down, to allow for the intelligibility of the speech. You can achieve this in real-time on your mix by using sidechain compression.

Many producers use tools that cause the entirety of an audio signal to be sidechained. As a result, the whole frequency spectrum of the audio becomes ducked. In our case, we’ll show you an alternative which in essence enables you to sidechain only certain frequencies.

As usual, we have prepared a short sequence in our SoundBridge: DAW. It contains most of the elements of a full mix, without the sub-bass for now. Let’s take a listen.

Sidechain compression session
~Full Mix – Without Sub Bass

As mentioned, this sequence lacks the sub-bass. This sound will be the perfect example to demonstrate the sidechain compression technique. After writing a simple MIDI sequence for the sub-bass, let’s hear it unprocessed together with the kick drum.

~Kick Drum & Bassline – Unprocessed

From the audio example above, we can hear that the sub-bass clashes a lot with the low frequencies of the kick drum. Instead of applying traditional sidechain compression where the whole signal gets ducked, we will apply a technique that will preserve the dynamics and tone of our sub-bass sound.

We will do this with the help of FabFilter Pro-Q 3. Let’s drag an instance of it to the sub-bass channel effect rack. In order for sidechain compression to be triggered by anything, we will have to enter the menu for it inside the SoundBridge effect rack. In the picture below you will see the corresponding “S” icon on the FabFilter Pro-Q 3 effect itself. This icon represents the sidechain setting. Once clicked, it takes us to a menu where we can choose what actually will trigger the sidechain. As you can see, we have chosen the kick drum as a trigger.

Sidechain menu SoundBridge

If we look at the picture below we can see there are now two analyzer images in the FabFilter interface. The grey one represents the sub-bass signal and the red one the kick drum. We can set this in the “Analyzer” section down below. This is really helpful to determine where exactly the two signals clash. In this case, it is clearly the area between 20 and 50 Hz.

FabFilter interface

In order to apply sidechain compression on just this particular area, we will add a new EQ band, and by right-clicking on the created frequency point select “Make Dynamic”.

At this point, the triggering is still not occurring. Instead, the compression is independent of the kick drum and reacts on the sub-bass itself.

FabFilter dynamic EQ

In order to fix that, we will have to enter another menu by clicking on the “AUTO” icon above the “Gain” knob.

Next, we have to click on the small icon right next to the Band 1 Threshold fader, which will actually engage the sidechain trigger.

We will set the threshold level to our liking and that’s pretty much it! Let’s listen to the difference now.

~Kick Drum & Bassline (Sidechain)
Threshold dynamic EQ

You can use this technique for just about anything, not just kick and bass.

Let’s hear our full mix with the sub-bass processed.

~Full Mix – Sub Bass (Sidechain)