You have probably heard about the side chain or side-chain technique in articles or videos about mixing, also known as “chaîne latérale” in French.
Invented in the 1930s by Douglas Shearer to control the sibilance of dialogue recordings in the film industry, this technique is now widely used because it allows for:
- improving how certain instruments stand out in a mix
- and generating interesting creative effects.
Primarily applicable to effects that intervene on the dynamics of the audio signal (compressors, noise gates…), the use of sidechain is particularly widespread in electronic music.
Typically, it’s thanks to sidechain that we can achieve
Not all compressors allow for sidechain operation, although it is becoming increasingly common (especially with plugins).
However, compression is not the only effect that can utilize sidechain.
Indeed, it is common to see noise gates or expanders that can use another signal as the sound source.
Similarly, some dynamic equalizers like FabFilter’s Pro-Q 3 also offer this option.
The 3 Types of Sidechain
To create a sidechain effect, there are three main possibilities that will lead to very different results.
Sidechain with a High-Pass Filter
The first option is the simplest, as it involves controlling a compressor (or any dynamic processor) with a signal identical to the track you want to compress, but filtered with a high-pass filter.
This primarily allows for the removal or attenuation of the low frequencies from the control signal.
But why do this?
Well, try compressing a drum buss. Every time the kick hits, your compressor will react strongly — indeed, the kick always contains a lot of energy.
This means that if you want to compress mainly the mids/highs for cohesion, your compressor might become too audible every time the kick comes in. And it will be crushed by the compression: typically, this results in a pumping effect.
Also, by filtering it in the control signal, it prevents the compressor from taking too much account of the dynamic variations in the lows, thus focusing on the higher frequencies.
To keep a clean kick while softening the overheads and snare, this is just the ideal technique! 🙂
Note: many compressors (hardware or software) have a default so-called “internal” sidechain feature, which corresponds precisely to this type of filtering.
Sidechain with an Insert Equalizer
In the same vein, one can also imagine sending the signal from the track to be compressed to an auxiliary track, the equalizer (with bell filters, low-shelf or high-shelf…) and using this filtered signal as the control signal.
Most of the time, I find this approach a bit complicated since you can already do a lot with a simple high-pass filter.
However, it remains an interesting possibility that allows for very precise adjustment of a compressor, noise gate, or expander’s behavior.
Sidechain Based on Another Track
This third sidechain technique is completely different from the first two.
Indeed, this time, we will use a control signal coming from another track or a group of tracks.
For example, we might compress the signal of a guitar track based on the level of the drum buss. Or, the signal of a synth pad based on the level of the kick track.
(The possibilities are endless…)
What is the benefit in this case?
Well, for example, it allows one track to be more audible compared to another.
I won’t say more, we’ll look at this in detail in the next paragraph… 😉
Uses of the Sidechain Technique
There are many ways to use sidechain during the production or mixing of a track.
However, two main types of uses generally stand out:
- sometimes, sidechain is used to help certain instruments find their place in the mix;
- and other times, sidechain is used more as a creative effect (for example, to give rhythm to a track)
Use #1: Highlighting a Kick
The most common use of sidechain will be to make a kick or bass drum stand out in the mix.
For example, compared to a bass track or a synth track.
Indeed, mixing bass is one of the most complicated aspects of mixing, especially if you want something clean with well-separated instruments in the low frequencies.
Thanks to sidechain compression, you will be able to compress your bass track every time the kick plays, which will help it stand out.
Here’s an example without compression of a situation where the kick is not standing out well compared to the bass track:
Now, with sidechain compression on the bass using the kick signal as the control signal, the kick stands out much better:
Effective, right?
Usage #2: Ducking the Voice
Thanks to the sidechain technique and relying on a noise gate, it is possible to generate what is called a ducking phenomenon: that is, the impression that one signal passes beneath another due to a constant attenuation.
Unlike sidechain compression, where we are dealing with variable attenuation (note, however, that the terms “ducking” and “sidechain compression” are sometimes used interchangeably…).
The best example of this usage is actually found at fairs.
You know, when the ride announcer announces the departure, the music lowers to a certain level while the message is being said and then rises again? 🙂
Well, that’s typically what is called ducking.
In the sound industry, this technique is mainly used for voice-overs. In audio mixing itself, it is much less common: one would rather rely on sidechain compression.
However, if you want to use this technique, you will need a gate that can work in reverse, in “ducking” mode as shown in the screenshot above:
- if the control signal is below the threshold, there is no attenuation;
- on the other hand, if the control signal is above the threshold, the attenuation defined by the Range setting is applied.
Compared to a compressor in sidechain mode, the advantage is twofold: on one hand, the attenuation is always the same, and on the other hand, you can take advantage of the Hold setting to keep the gate closed.
Usage #3: Adding Dynamics to a Mix
In many cases, using sidechain can bring a new dynamic to certain crucial moments in a mix.
Let’s listen to this passage from the song “Borderline” by Trevor de Clerq:
We are exactly at a moment where two atmospheres clash: a slow, acoustic atmosphere at first, and something more aggressive with the entry of the guitars.
The problem is that the sharp entry of these instruments creates a psycho-acoustic phenomenon that will mask, in particular, the impact of the kick drum.
As a result, it sounds a bit flat.
But look at what happens when I put a compressor using the full drum buss signal in sidechain, and I automate it to only intervene at the first beat of the guitar entry:
Well, for the example, I deliberately exaggerated the manipulation (we’re still at about ten dB of gain reduction!) — but this time the first kick + cymbal hit stands out much better, and the transition feels much more alive.
In short, you get the idea: the sidechain technique can help control the dynamics of a mix at key moments.
Usage #4: Adding Rhythm to a Track
Using sidechain with a compressor, expander, or noise gate can also allow for all sorts of creative effects.
For example, we often hear in electronic music synth pads that are filtered through a gate to create rhythmic patterns, directly linked to the drum machine.
A bit like this:
Here, the audio example is very clear, but of course we can imagine something more subtle to create movement on a pad or on any sound source.
I am particularly thinking of field recordings, like this recording of the magnetic field from an infrared door sensor (yes 🙂 !):
Tip: for this type of use, you really need to pay attention to the attack and release settings applied, as these will control the rhythmic effect.
Usage #5: Sidechain with a ghost track
Do you know about ghost tracks?
This is a fairly advanced mixing/production technique that obviously uses a compressor in sidechain mode.
In the examples we saw earlier, the control signals (to remind you, these are the signals that will trigger the compressor in sidechain mode) were always audible.
However, it is completely possible to trigger sidechain compression without the control signal being audible.
Typically, you can imagine a percussion track that would give a certain rhythm to a synthesizer pad without the beat being audible.
Or, it is also possible to use this technique to trigger a compressor on a track earlier than it should: in this case, the ghost track will be identical to the original track but will be played a few milliseconds earlier…
How to do a SideChain?
To make this guide as complete as possible, here is how to do a sidechain in several of the main sequencers, namely:
- Ableton Live
- FL Studio
- Cubase
- Studio One
- Pro Tools
(If you have another one, feel free to contact me so we can complete the article together 😉 )
How to do a sidechain in Ableton Live?
Select the Ableton Live compressor and add it to the track you want to compress:
Display the hidden additional options on the left of the effect module by clicking on the small arrow:
Activate the sidechain by clicking on the “Sidechain” button, which turns yellow, and choose from the dropdown menu “Audio From” the track you want to use as the control signal:
Then all you have to do is play with the ratio, threshold, and other compressor parameters to hear your compression.
Note that it is possible, to check, to listen to the control signal by clicking on the headphone icon just next to the “Sidechain” button.
How to do a sidechain in FL Studio?
In FL Studio, start by adding your compression plugin. Here, I will take the Fruity Limiter (in ‘compressor’ mode).
Open the mixer view (F9) and select the source track (so the control signal). Then, while keeping this track selected, right-click on the arrow symbol located at the bottom of the target track and choose “Sidechain to this track”:
All that remains is to properly set the compressor by choosing “1” in the “Sidechain” menu of the plugin:
How to do a sidechain in Reaper?
In Reaper, the procedure for doing a sidechain may seem a bit more complex but it is not that complicated.
First, add a compressor (here the ReaComp compressor) to your target track:
Then, drag and drop the routing symbol from the source track (control signal) to the target plugin interface.
Check in the window that opens that the routing is correct in channels 3/4:
Finally, in the case of ReaComp, select “Auxiliary Input” at the “Detector Input” setting so that the signal is taken into account by the compressor:
How to do a sidechain in Cubase?
To set up a sidechain in Cubase, the first step is as usual to add a compatible plugin (here, the default compressor of the sequencer) and to activate the sidechain option, which is a small orange icon:
Then, at the level of the track corresponding to the control signal, you need to do as if you were adding a send effect, but by choosing the appropriate sidechain channel:
And there you go 🙂
If needed, the level of the control signal can be adjusted directly at the send effects level:
(Thanks Gil for the screenshots!)
How to do a sidechain in Studio One?
Add a compressor like the one from PreSonus on the track you want to compress and click on the “Sidechain” button located in the upper bar of the plugin:
In Console view (F3), expand the effects panel on the concerned track and add a new “Send” by choosing the track corresponding to the control signal from the “Sidechain” list that appears:
If needed, you can adjust the level of the control signal directly at the “Send”:
And there you go, everything is ready! 🙂
How to do a sidechain in Pro Tools?
In Pro Tools, let’s take the example of the basic compressor of the software. If you add it to a track, it looks like this:
Create a new bus (here, Bus 17), then:
- activate the sidechain of the plugin by clicking on the key symbol on the right
- select the bus you just created at the other key symbol, at the top left:
Then you just need to send the control signal to the specified bus and adjust its level:
(Thanks Luc for the screenshots!)
In conclusion
There you go, you now know pretty much everything about the sidechain technique and how to implement it on most DAWs! 🙂
However, to ensure you make the most relevant adjustments, feel free to read (or reread) my guide on audio compression, which details the main settings of compressors.