Sidechain Compression Explained

Sidechain Compression Explained - What is Sidechain Compression

One thing that sets a beginner producer apart from an engineer is the proper use of compression.

Professionals understand compression deeply, and know where to use its various forms. If you’re looking for the next step to make your mixes greater, look no further.

In Sidechain Compression Explained, we’ll dive into how sidechaining works, and how you can use this simple, yet noticeable effect to take your tracks to the next level.

Compressors 101

Waves Audio C6 Multiband Compressor
The Waves Audio C6 Multiband Compressor, commonly used for sidechaining. Read more about it here.

Let’s briefly review the function of a compressor before getting into how to sidechain. The main job of an audio compressor job is to amplify/attenuate the peak volumes of a track in order to create volumes closer to the overall average volume.

For example, if a kick drum’s volume was significantly louder than the other percussion on a track, a compressor would reduce its volume in order to match its levels to the other percussion sounds.

Compression allows for a mix to sound cleaner and more cohesive. However, compressors can leave a mix lacking energy if not blended correctly. Studio professionals often employ a method called parallel compression in order to solve this issue.

Parallel compression takes both the compressed signal and raw track and melds them together. Both basic and parallel compression can be used in conjunction with sidechaining, and allowing for a bevy of musical possibilities.

If you need to understand more about parallel compression, take a look at this previous article where we discuss it in more detail.

Compressor Common Uses

Compressors are very versatile and have a couple of universal parts. Let’s review them briefly. For a more in depth description, see our Compression Explained article.

  • Threshold: Determines at what point or volume the compressor should begin compressing
  • Ratio: Determines the intensity of the compression applied to a track
  • Attack: How fast the compressor is applied to a track
  • Release: How fast the compressor stops applying compression to a track
  • Knee: Determines the speed of transition from raw signal to compressed track
  • Make-up gain: Used to increased lost amplitude after a track has been compressed
  • Input/Output: Used for routing and other various effects, including sidechaining

Keeping these components in mind, let’s take a look at three of the most common uses for compressors:

Reducing peak transients – The most common and basic function of a compressor is to reduce volume spikes, and raise signals significantly softer than the rest of the mix. Since vocals are often dynamic with varying levels of volume and energy, compressors are often applied to vocal busses to smooth out the levels.

Creating a fuller sound – Compression is also used to create a wider, or fuller sound, and capture the energy of a particular recording. Parallel Compression works to reduce peaks, but also amplify the moments in a track where raw energy should be recognized.

Creating space in the mix – Sidechain compression allows for the engineer to create space in a mix. It works by temporarily reducing the amplitude of certain frequencies so that a frequency is not overbearing in a mix at any particular moment.

What is Sidechain Compression?

Sidechain compression is essentially regular compression with more specific automation. It works to duck the volume of a particular frequency to create space for another instrument/expressed signal.

For example, if we have a kick coming in at about 80 Hz for beats 1-4, and a bass sound also around 80 Hz, we can use sidechaining to make space for the kick to be heard. If there are too many instruments/sounds at a particular frequency, the mix tends to sound muddy, unbalanced, and unprofessional.

By sidechaining the bass to the kick, we program the compressor to reduce the volume of the bass everytime that the kick comes in (beats 1-4). Many DAWS include a frequency stock plugin of some sort allowing you to be as precise as possible with which frequencies need to be balanced. Moreover, a simple equalizer (EQ) can assist in this process, and show you where you may need to sidechain out certain frequencies to achieve a cleaner mix.

How to set up Sidechain Compression

Begin by determining which sounds need to duck out or “breathe” at a certain point. A common problem area that can be resolved with sidechaining is having a kick and bass sound at similar frequencies.

With your two different sounds/signals, determine which one you want to highlight. This will be the track you route the compressor to. The compressor will be placed on the track that you are trying to duck the sound from. With our kick and bass example, one would place the compressor on the bass track and route to the kick as we are working to highlight the kick sound.

Select a compressor of your choosing that has sidechaining capabilities. Most DAWs come with one of these built in, but there are also many inexpensive external plugins you can purchase that have sidechain as a function.

Find the sidechain button and engage it. There should be a section that asks what input signal you’d like to use. In our example, this would be the Kick. The input signal is what is being highlighted in the mix.

Adjust the parameters accordingly. Oftentimes, sidechaining involves a fast attack and low threshold depending on the goals of the producer. Have fun trying out different combinations!

You have officially engaged sidechain compression. The track should seem like it breathes a little better, and grooves a bit more.

Common Uses of Sidechain Compression

Drums – By far the most common use of sidechain compression, sidechaining is often used to make drums, the kick in particular, shine especially when coupled with heavy synths, bass, and subbass. The human ear is better at discerning higher frequencies than lower frequencies, so it makes sense that professional engineers focus sidechain compression on the low end of the mix.

Read more on how to compress drums.

Vocals – With endless possibilities and vocals being unique as a fingerprint, sidechain compression is often used to help vocals stand out in the mix. An engineer can use an EQ to determine where a boost is needed, and duck out frequencies conflicting with the vocal.

Read more on how to compress vocals.

Ghost Compression – A technique commonly used in EDM music, ghost sidechain compression involves sidechaining a track to a track that has no volume. This produces an effect where the synth or instrument sidechained to has the signature volume duck, but with no presence of the sound it was linked to. It can help tracks breathe in a unique way, and opens the door to new effects.

Here is an example of ghost compression in a EDM track. Notice that “pumping” sound is due to sidechaining (sidechain compression starts around 44 seconds in).

For futher uses, take a look at Ableton’s blog for some interesting tips.

Overall, sidechaining gives you more control than basic compression, and can help you stand out as a producer. Sidechain compression allows for your sound to breathe, groove, and ultimately, feel more. Be sure to give it a try on your next mix.