Does your kick vanish under the bass? Sidechain compression fixes that by letting the kick briefly turn the bass down, so both fit in the same low end.
| Setting | Typical starting value |
|---|---|
| Attack for ducking | Fast, under 10ms |
| Release for subtle ducking | 20ms to 75ms |
| Release for obvious pumping | Slower, timed to the tempo |
| Typical use | Kick triggers compressor on bass |
These figures come from a Sonarworks guide. They are starting points and can change, so check the source before you rely on them.
This technique sits within wider music production practice, and it builds on ordinary compression.
What sidechain compression does
A normal compressor turns a sound down when that same sound gets loud. With a sidechain, the compressor listens to a different signal than the one it turns down.
That second signal is often called the key or trigger. It is never heard through the compressor itself. It only tells the compressor when to act.
In a kick-and-bass setup, each kick briefly lowers the bass level to make its attack clearer.
If you are new to compressors, read how to use a compressor first, since threshold, ratio, attack and release work the same way here.
Why kick and bass need it
Two instruments often fight in the same range. The guide notes that “two or more instruments often compete for attention in the same frequency range, like a kick drum and sub-bass.”
When both play at once, the low end turns heavy and the kick loses its front edge. You may turn the kick up, but then the whole mix gets louder and has less headroom.
You could carve out frequencies with EQ. The alternative is to “duck the level of the bass to make room for the transient burst of the kick drum.”
The same idea works elsewhere, for example:
- Pads or synth chords ducking under a lead vocal.
- Reverb or delay tails ducking under the dry vocal.
- Guitars or keys stepping aside for a busy snare pattern.
- Any crowded track that should step aside for a more important one.
Setting it up step by step
Most digital audio workstations work the same way, though the menu names differ. The Sonarworks guide uses a bass guitar and a kick drum.
- Insert a compressor on the bass track, one with a sidechain or key input.
- Set the sidechain input of that compressor to listen to the kick track.
- Adjust threshold and ratio so the bass is compressed by the amount you want each time the kick hits.
- Tweak attack and release to taste.
The guide says the same setup can be used for any tracks, so the steps carry over to vocals, pads or buses. Place the compressor on the track you want to duck, select the trigger track, and adjust the settings to suit.
Keep your levels healthy before the compressor. Good gain staging makes the threshold behave predictably, because the trigger level decides when ducking starts.
Reading threshold and ratio
The threshold sets how loud the trigger must be before the compressor reacts. A lower threshold means more of the kick crosses it, so ducking happens more reliably.
The ratio sets how hard the bass is turned down once that happens. A gentle ratio gives a small dip. A high ratio gives a deep, obvious drop.
A practical way to work is to start with the compressor’s gain-reduction meter in view. Play the loop and watch the meter move with every kick, then adjust until the bass dips by an amount you can hear but would not call a special effect.
Always judge the result with the whole mix playing. A setting that sounds right on the soloed kick and bass can feel too heavy or too weak in context.
Attack and release: subtle or pumping
Timing decides whether the effect is invisible or obvious. The guide says that in most cases you want a fast attack time so the audio ducks quickly.
For release, the guide says short times are best for subtle ducking effects. Slower release times, timed to the tempo of the track, are best for obvious pumping.
MusicRadar’s bass and kick tutorial also says to make sure attack is “set fast rather than slow.”
Here is a quick way to think about it:
- Attack too slow: the kick and bass still clash before the compressor reacts.
- Release too short: the bass may snap back too quickly and sound choppy.
- Release too long: the bass has not recovered before the next kick, and the mix feels squashed.
Tempo matters too. For fast tracks, use a faster release. For sustained notes, a slightly slower release can work, but the guide warns against “unwanted pumping effects from too-long release times.”
Pumping as a creative effect
Sometimes you want to hear it. Dance producers also use pronounced ducking as a rhythmic effect.
To hear the extreme version, MusicRadar suggests turning the threshold “all the way up to -50” and raising the ratio too. Then back off until it grooves with the track.
For this use, set the release so the bass swells back in time with the beat. Pads and chords are good targets, because the movement gives a static part a rhythm of its own.
Use it with restraint on acoustic or live-feeling styles. A pump that suits a club track can sound like a fault on a folk recording.
Common mistakes to avoid
The most frequent error is ducking too much. If the bass disappears on every beat, the groove loses its weight, and listeners hear a hole rather than a clean kick.
Another is forgetting that the trigger must be routed correctly. If the compressor reacts to the bass itself, it may still compress the bass, but the kick will not control the ducking.
Check these points when the result sounds wrong:
- Is the compressor really listening to the kick, and is its sidechain or key input switched on?
- Does the gain-reduction meter move in time with each kick?
- Does the bass come back before the next hit, or does it stay buried?
- Does the effect still sound right when you hear the full arrangement?
If the kick is muted or its level is changed later, the ducking can change too, depending on where the signal is tapped. Recheck the effect after any big change to the drums.
Finally, trust your ears over any number. The values in this guide are starting points, and every kick and bass sound responds a little differently.
A simple workflow to practise
Practice on a short loop with just a kick and a bass line. Keep it simple until you can hear what each control changes.
- Mute everything except the kick and bass.
- Set the compressor’s ratio high and the threshold low so the ducking is easy to hear.
- Shorten the attack until the kick punches through cleanly.
- Lengthen the release until the bass returns smoothly in time with the beat.
- Back off the ratio until the effect is felt rather than noticed, then unmute the rest of the mix.
Making an exaggerated version first is a useful habit. Once you know how the extreme setting sounds, it becomes easier to place the final setting where you want it.
Frequently asked questions
Do I need a special compressor?
Show answer
You need one with a sidechain or key input, as the Sonarworks guide says. Most DAW stock compressors have one.
How fast should the attack be?
Show answer
Start fast, under 10ms, so the bass ducks as the kick arrives. Slow attacks let the two clash first.
How do I stop audible pumping?
Show answer
Use short release times, from 20ms to 75ms, and keep the ratio gentle. Longer releases are what make pumping obvious.
Can I use it on things other than kick and bass?
Show answer
Yes. The guide says the same setup can be used for any tracks, such as a vocal and its reverb.
