What is Sidechain Compression?
Sidechaining is a production technique that involves taking an audio source such as a kick drum track for example and using that signal as a trigger for controlling effects on a secondary track.
Sidechain Compression is where the effect being controlled is a compressor. This allows the volume of the secondary track to be lowered or ‘ducked’ when triggered by the primary audio source.
In this article we’ll cover the basics of sidechain compression, including when and how it should be used, together with an example. We’ll be using Ableton Live, but the techniques are applicable to any DAW that has a stock compressor that supports sidechaining (which is pretty much all of them). I’ll also be recommending some great 3rd party plugins to use as an alternative.
Let's crack on...
Why use Sidechain Compression?
The most common use for Sidechain Compression is in a situation where an instrument is losing its impact due to competing frequencies with another track. For example, if your bassline and kickdrum are close together on the frequency spectrum, then the impact of the kick will be lessened. Ducking the bass each time the kick hits will help the kick stand out and give it more punch.
The second use case could be due to frequency build-up issues. In the example above, the combined loudness of your kick and bass tracks will be greater each time the kick hits. If you are ducking the bassline however each time the kick plays, then this reduces their combined volume, giving you space in your mix and ultimately allowing you to increase the overall loudness.
Sidechaining can also be used creatively to get some awesome sounding effects. Instead of sidechaining to a straight kick drum for example, why not add additional offbeat triggers or ghost hits to your sidechain trigger. You can also combine a sidechain with delays or reverb sends to create some really interesting effects. A prominent sidechain can also be used to produce that French House style sound popularised by bands such as Daft Punk:
How to use Sidechain Compression
Let's have a closer look now at how to use sidechain compression in Ableton Live.
In the project below I've got three groups of instruments: a drum group, a synths group, and a vocal group. In addition, I've created a muted sidechain or SC track. The reason for this additional track is that sometimes the kick you're using may be too phat to achieve the ducking effect that you want. Utilising a shorter rim-shot or click will give you a tighter, more controlled sidechain.
Have a listen first to a section of the track without any side-chain compression. Notice specifically how the kick is not really cutting through the mix with enough punch.
To improve this I'm going to grab the Ableton stock compressor (from the browser search for Audio Effects -> Compressor), and drag it on to the synth group. Clicking the arrow in the top right allows me to then activate the sidechain mode and select the audio source, which in this case is the track I've named 'SC'. Note that it doesn't matter that this track is muted, it will still receive the trigger information.
Within the Ableton compressor there are three different views: the default collapsed view, the transfer curve view, and the activity view. I'm going to select the activity view as it's useful for visualising what happens with the signal over time.
The first thing I'm going to do now is play with the threshold setting by dragging down the blue line. I can immediately hear the effect this has on the sound and see the effect in the waveform display.
Now I'm happy with the compression threshold I'm going to adjust some of the other controls.
The attack knob controls how long it takes to reach maximum compression after the signal exceeds the threshold. There is no optimum value here, however if you want the initial part of the kick transient to be less defined, turn the attack up. I'm going to leave this at the default setting.
The ratio control sets the ratio of compression between the input and output. For a more natural ducking effect, it's best to start with a ratio setting of 2:1 or 4:1 and experiment from there.
The release control effects how quickly the ducking effect comes back. I'm going to adjust the amount whilst listening to the track and watching the waveform display. I'm happy in this case with around 50ms.
Now I'm happy with the side-chain effect I'm going to copy it over to the vocal group. Note that because the vocals are higher in frequency than the bass and synths, I'm going to apply less compression here as they are less likely to interfere with the kick.
Let's have a listen to the results. Although fairly subtle, you should be able to tell that the kick is now cutting through the mix with slightly more punch.
Best 3rd Party Sidechain Plugins
Note that some of the plugins below do not take an audio source as a trigger, but instead use customisable waveforms to produce the ducking effect, however they are still commonly referred to as sidechain (or sidechain emulation) plugins.
Kickstart by Nicky Romero
Kickstart by Nicky Romero is a simplistic plugin that uses pre-defined waveforms to apply ducking to your tracks. In that sense it's not really a sidechain plugin, but more of a volume automation utility without the need for a separate sidechain signal. You won't get the level of control here that you would with standard sidechain compression, however it's still a popular option due to its simplicity and very reasonable price point.
LFO Tool by Xfer records
LFO Tool by Xfer Records is an incredibly versatile plugin. Not only does it function as a standard sidechain compression emulator but also allow you to create trance-gate, auto-pan, tremolo and wobble type effects enabled by the insane amount of control you have over the shape of the LFO shape. It has an impressive set of inbuilt presets; however, you can also set the plugin to trigger from an external source. Perhaps not the prettiest of user interfaces, but for all these features at such a low price you really can't complain.
Trackspacer by Wavesfactory
Trackspacer by Wavesfactory features a 32 band EQ that reacts dynamically to an incoming audio signal. It then applies an inverse EQ to those specific frequencies monitored in the sidechain signal. This allows a very targeted approach to adding space within your mix. It's a little bit more expensive than other options, however the precise control it gives you, combined with its gorgeous UI and ease of use makes it a great choice.
I hope you enjoyed this brief introduction to sidechain compression.
Leave a comment if you have any of your own tips or tricks on how to use sidechain compression, or let me know what you favourite 3rd party sidechain plugin is.
Have a great day and Happy Producing!