Sidechain compression is when a compressor on one track is triggered by a different track. The classic example: every time the kick hits, the bass dips in volume for a split second, so the two stop fighting over the low end. Turn the effect up and you get the famous “pumping” sound of dance music; keep it subtle and it quietly makes room in almost any mix.
This guide explains what sidechaining is, how to set it up in any DAW, what each compressor setting does in a sidechain context, and the most useful ways to use it, from kick-and-bass ducking to keyed gates, ducked reverbs and multiband tricks.
What Is Sidechaining?
A normal compressor listens to the same audio it’s processing. When that signal gets louder than the threshold, the compressor turns it down. (If you need a refresher on the basics, start with our guide on how to use a compressor.)
Inside every compressor there’s a detector circuit that decides when to act. The signal feeding that detector is called the sidechain. Normally it’s just a copy of the track itself. An external sidechain (often labeled “key,” “SC” or “ext”) lets you feed the detector from another source instead. The compressor still only processes the track it’s sitting on; the key signal is never heard through it. It just tells the compressor when to work.
That idea isn’t limited to compressors. Gates, expanders, multiband compressors and dynamic EQs can all be keyed from another track, and they all count as sidechaining. In practice, you’ll use it two ways:
- Ducking: a compressor turns the target track down whenever the key track plays (kick ducks bass, vocal ducks guitars).
- Keyed gating: a gate lets the target track through only when the key track plays (a snare hit opens a gate on a noise burst, for example).
Why Use Sidechain Compression?
Most mix problems sidechaining solves come down to two sounds wanting the same space at the same moment. You could turn one of them down or EQ it permanently, but that weakens it the whole time, even when nothing is in its way. Sidechaining only gets out of the way when it needs to. Common reasons to reach for it:
- Clarity: let the kick punch through the bass, or the vocal sit on top of dense guitars or synths.
- Groove: create rhythmic movement (pumping) on pads, chords or a whole group of tracks.
- Automatic level riding: duck music under a voice-over, or a reverb tail under the dry vocal, without drawing automation.
- Sound design and repair: use a keyed gate to add snap to a snare or sub to a kick, or to lock a part to a rhythm.
How to Set Up Sidechain Compression in Any DAW
Most DAWs support sidechain routing, and many stock compressors include a sidechain input, so you probably don’t need to buy anything. The menus differ from program to program (check your DAW’s manual for the exact clicks), but the process is the same everywhere. If you’re still choosing software, our guide to what a DAW is and how it can help you is a good place to start.
- Pick the key and the target. The key is the sound that should win (the kick). The target is the sound that gets out of the way (the bass). The compressor always goes on the target.
- Insert a compressor with a sidechain input on the target track. Look for a sidechain, key or SC selector in the plugin header or settings.
- Route the key signal to it. Some DAWs let you pick the source track straight from a dropdown in the plugin; others have you create a send or bus from the key track to the compressor’s sidechain input. A pre-fader send keeps the trigger level independent of the key track’s fader.
- Switch the compressor to external sidechain. Some plugins keep listening to their own input until you enable this, even after the routing is in place.
- Set threshold, ratio, attack and release (details below), watching the gain-reduction meter.
- Judge it in the full mix, not in solo, and toggle the compressor on and off to make sure it’s actually helping.
Sidechain Compressor Settings Explained
These are the same controls you’d use for any compression, but in a sidechain setup they react to the key signal, not the track you hear. The numbers below are starting points to tweak by ear, not rules.
Threshold
Sets how loud the key has to get before the target is turned down. Lower the threshold until the gain-reduction meter moves on every hit you want to trigger it. Because the threshold follows the key, changing the key track’s level (or its sound) changes how much ducking you get.
Ratio
Controls how hard the target is pushed down once the key crosses the threshold. Something like 2:1 to 4:1 works for subtle, invisible ducking. Higher ratios (around 4:1 up to 10:1 or more) give a deep, obvious dip, which is what you want for pumping.
Attack
How quickly the compressor clamps down after the key crosses the threshold. For kick-and-bass ducking you usually want a fast attack (roughly 0.1 to 5 ms) so the bass is already out of the way when the kick’s transient lands. If your compressor has a lookahead option, it can help catch the very start of the hit. A slower attack lets a little of the target’s onset slip through, which can sound more natural on vocals and guitars.
Release
How quickly the target comes back up, and the setting that shapes the feel more than any other. Too short and the bass can click or distort as the gain chases the waveform; too long and the target never fully recovers, so the track loses energy. A good habit is to time the release to the tempo so the target is back just before the next hit. At 128 BPM, a quarter note lasts about 469 ms (60,000 divided by 128), so a release a bit shorter than that is a sensible place to start for four-on-the-floor ducking.
Range, Knee and Sidechain Filter
A range (or depth) control caps the maximum gain reduction, which is handy for keeping ducking polite. A softer knee makes the onset gentler. Many compressors also include a filter on the sidechain signal: if you key from a full drum bus, a low-pass on the sidechain lets mostly the kick trigger the compressor, while a high-pass does the opposite.
As a rough guide, a few dB of gain reduction (say 2 to 4 dB) is usually enough for ducking you feel more than hear. Pumping typically means 6 dB or more.
Kick and Bass: The Classic Use
Kick and bass share the same low-frequency territory, roughly 40 to 120 Hz depending on the sounds. When both hit at once, their energy stacks up, eats headroom and blurs the kick’s punch. EQ helps by giving each its own pocket (our guide on how to use EQ covers that), but sidechaining handles the moments when they still collide.
Put the compressor on the bass, key it from the kick, use a fast attack and time the release to the groove. In rock, pop, hip-hop and R&B, keep it subtle so the bass still feels steady and the kick simply reads more clearly. In house, techno and other dance styles, push it further until the bass visibly breathes with the kick.
- Multiband ducking: if ducking the whole bass makes it disappear, use a multiband compressor keyed from the kick and duck only the low band. The bass’s upper harmonics and growl stay put, so it still cuts through on small speakers.
- More than one bassline: decide which bass is dominant (it can change between sections) and key the secondary bass from it. Keep the kick ducking first in the chain, since it’s the most frequent trigger.
The Pumping Effect
Pumping is sidechain compression used as an obvious effect: pads, chords, reverb returns or even a whole group of tracks dip on every kick and swell back in between, creating that breathing feel heard all over house and EDM. To do it cleanly, route the elements you want to pump to one bus and sidechain the bus, so everything moves together. Use a higher ratio and set the release so the swell lands in time with the groove.
The one rule: it has to add energy. Pumping everything can flatten a drop instead of lifting it, so leave some elements, usually the drums and lead vocal, untouched and A/B the result honestly.
Ghost (Trigger) Tracks
A ghost track is a kick pattern (or any short sound) that exists only to feed the sidechain; you never hear it. It’s worth setting up because:
- the ducking keeps going through breakdowns when the real kick drops out;
- you can change the audible kick’s sound, level or pattern without changing the ducking;
- you can program a different rhythm for the pump, such as off-beat or half-time hits.
Be careful how you silence it: in some DAWs, muting a track also stops it feeding the sidechain. Routing its output to nowhere, or using a pre-fader send with the fader down, usually avoids the problem; check how your DAW handles it. You can also experiment with a processed trigger, such as a delayed copy of the kick, for syncopated movement.
Volume-Shaper Alternatives
You can get the same result without any routing. Tempo-synced LFO or volume-shaping plugins let you draw the duck curve directly onto a track, and you can always draw volume automation by hand. These give you a perfectly repeatable shape that doesn’t depend on a trigger’s level and keeps working when the kick drops out. The trade-off is that they don’t respond to what’s actually playing, so fills, variations and half-time sections get the same shape regardless. Many producers use a shaper for the obvious pump and real sidechain compression for subtler, responsive ducking.
Creative Sidechaining Beyond EDM
Duck Guitars, Keys or Pads Under the Vocal
In a busy chorus, key a compressor on the guitar or synth bus from the lead vocal and aim for just 1 to 3 dB of reduction with a moderate attack and release. Nobody should hear it working; the vocal just seems to sit on top more easily. For an even more transparent result, use a multiband compressor or dynamic EQ and duck only the vocal’s presence range (roughly 1 to 4 kHz) in the instruments, leaving their body and sparkle alone.
Duck Reverbs and Delays
Put a compressor on your vocal reverb or delay return and key it from the dry vocal. While the singer is singing, the effect pulls back and the words stay clear; in the gaps, the tail blooms to fill the space. It’s one of the most useful mix tricks there is, and it works on guitar solos and lead synths too.
Voice-Over and Podcast Ducking
The same idea works outside music: put the compressor on the music bed, key it from the voice, and the music dips automatically whenever someone talks.
Keyed Gates
A gate keyed from another track opens only when the key plays, which opens up a whole set of tricks:
- Snare snap: run white noise (or a bright sample) on its own track with a gate keyed from the snare. Use a fast attack and short hold and release, then blend it in under the snare for extra crack.
- Kick sub: gate a low sine tone, tuned to the song’s key, from the kick to add weight to a thin kick.
- Rhythmic pads: key a gate on a sustained pad from a hi-hat or percussion pattern for a choppy, trance-gate style rhythm.
- Lock the bass to the kick: key a gate on the bass from the kick so it only speaks with the kick. Use it sparingly; it can sound chopped.
Multiband and Dynamic EQ Sidechaining
Keying just one frequency band is the most surgical form of sidechaining. Duck only the sub of the bass under the kick, only the 2 to 5 kHz region of a guitar bus under the vocal, or only the snare’s frequency range in a busy breakbeat loop when you layer a programmed snare on top. Many dynamic EQs and multiband compressors accept an external sidechain, so a single band moves while the rest of the sound stays untouched.
De-Essing and the Internal Sidechain Filter
A de-esser is really a sidechain trick. The compressor’s detector listens to an EQ’d version of the vocal that emphasizes sibilance (somewhere around 4 to 10 kHz, depending on the singer), so it only reacts to harsh “s” and “t” sounds. Split-band de-essers then turn down only the high frequencies. The same principle explains why a high-pass filter on a bus compressor’s sidechain is so useful: it stops the kick and bass from driving all the gain reduction.
Common Sidechaining Mistakes
- Too much, everywhere: if the whole mix pumps when it shouldn’t, back off the ratio or range.
- Release too short on bass: listen for clicks or distortion and lengthen it.
- Forgetting the key’s level matters: turning the kick down post-fader can quietly change your ducking. Use a pre-fader send or a ghost track.
- Setting it up in solo: ducking only makes sense in context.
- Using it to fix everything: sometimes a better EQ decision or an arrangement change (moving a part, changing an octave) solves the clash more cleanly.
Wrapping Up
Sidechain compression comes down to one idea: let one sound control another. Start with kick and bass, get comfortable with threshold, ratio, attack and release, and then try ducked reverbs, keyed gates and multiband tricks. Keep checking your work on more than one system, and remember that sidechaining won’t rescue a weak mix later; as we explain in They’ll Fix It in the Master: True or False?, the real fixes happen while you mix.
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