Sidechain Compression: The Complete Guide

Sidechain compression is one of the most useful techniques in modern production. It's also one of the most misunderstood.

Here's how it actually works and when to use it.

What Sidechain Compression Actually Does

Normal compression: the compressor listens to the signal it's compressing. When that signal gets loud, it compresses.

Sidechain compression: the compressor listens to a different signal. When that signal gets loud, it compresses.

Example: You put a compressor on your bass. You sidechain it to your kick. Every time the kick hits, the bass ducks out of the way. The kick punches through clearly, then the bass comes back.

That's it. That's sidechain compression.

The Two Main Uses

1. Kick/Bass Separation

Kick drums and bass live in the same frequency range. They fight for space. One of them has to move.

Sidechain the bass to the kick. Every time the kick hits, the bass ducks by 3-6dB for a split second. The kick punches through. The bass fills the space between kicks.

Your low end stays powerful but defined. No mud, no masking.

2. The Pump Effect

That rhythmic breathing you hear in French house, EDM, and pop music? That's aggressive sidechain compression.

Daft Punk made this famous. The whole mix pumps against the kick. It's not subtle—it's an effect.

Same technique, more extreme settings.

How to Set It Up

Step 1: Add a Compressor to the Track You Want to Duck

Put a compressor on your bass track (or synth, or whatever you want to duck).

Step 2: Route the Kick to the Sidechain Input

This varies by DAW, but the concept is the same. You're telling the compressor "listen to the kick, not the bass."

In most DAWs, there's a sidechain dropdown in the compressor where you select the input source.

Step 3: Dial In Your Settings

For subtle kick/bass separation:

Ratio: 4:1 to 6:1
Attack: 0-5ms (fast—you want it to duck immediately)
Release: 50-150ms (tune this to your tempo)
Threshold: Adjust for 3-6dB of gain reduction

For the pump effect:

Ratio: 8:1 to 10:1 (or higher)
Attack: As fast as possible
Release: Longer—200-400ms, or sync to note values
Threshold: Adjust for 6-12dB of gain reduction

Step 4: Tune the Release to the Tempo

This is crucial. The release determines how long the duck lasts and how it feels rhythmically.

Too fast: choppy, unnatural
Too slow: the ducked signal never comes back fully before the next kick

For most tempos, 100-200ms works for subtle separation. For the pump effect, match it to eighth notes or quarter notes.

Pro Tip: Sidechain to a Ghost Kick

Here's a trick the pros use: instead of sidechaining to your actual kick, create a duplicate kick track that you mute. Sidechain everything to that ghost kick.

Why? Now you can change your actual kick sound, add fills, or mess with the pattern without affecting your sidechain pumping. The ghost kick stays consistent.

Sidechain EQ: The Surgical Alternative

Sometimes sidechain compression is too heavy-handed. You want the bass to duck, but only at the specific frequencies where the kick lives.

Enter sidechain EQ (or dynamic EQ with sidechain).

Put a dynamic EQ on your bass. Create a cut at the kick's fundamental frequency (usually 50-80Hz). Sidechain it to the kick.

Now, only that specific frequency ducks when the kick hits. The rest of the bass stays put. Way more transparent than compressing the whole signal.

This is my preferred method for most mixing situations. Full sidechain compression is better for the obvious pump effect.

What to Sidechain

Almost Always

Bass to kick
Sub bass to kick
808s to the kick transient

Often

Pads and synths to kick (subtle ducking keeps them out of the way)
Reverb returns to vocals (keeps reverb from masking the dry vocal)

For Effect

Entire mix to kick (the pump)
Synth arps to kick (rhythmic breathing)
White noise risers to kick

Common Mistakes

Release Too Fast

The signal comes back too quickly and you get a choppy, clicking sound. Slow down the release.

Release Too Slow

The signal never fully recovers between kicks. Your bass (or whatever) sounds constantly quiet. Speed up the release.

Too Much Gain Reduction

Unless you're going for the pump effect, 3-6dB is usually enough. More than that and things start sounding weird.

Sidechaining Everything

Not everything needs to duck. If your mix is pumping when you don't want it to, you've overdone it.

Without a Compressor: Volume Automation

Before sidechain compression, engineers did this manually with volume automation. You can still do it—draw volume dips on the bass that align with the kicks.

It's more work, but it gives you complete control. Some mixers prefer this for acoustic/organic music where the pump effect would sound unnatural.

The Bottom Line

Sidechain compression is simple: make one thing duck when another thing plays.

For kick/bass separation, use subtle settings (4:1, fast attack, 100ms release, 3-6dB reduction).

For the pump effect, go aggressive (10:1, fastest attack, synced release, heavy reduction).

Try both. See what your track needs.