Sidechaining

Sidechaining sends one signal to trigger a processor on another signal. The most famous use: kick drum sidechained to a bassline so the bass ducks every time the kick hits, creating that pumping, breathing dance-music rhythm.

The same technique solves real mix problems. Sidechain a vocal-bus to duck a synth pad whenever the singer is singing, and you'll never need to manually ride the pad's volume again.

How It Works

A compressor normally listens to its own input to decide when to compress. A sidechain input lets you say "listen to this other signal instead of your input. When it crosses the threshold, compress my actual input."

The processed signal isn't the trigger; the trigger isn't processed. They're independent.

The Pumping Effect

The classic dance-music sidechain:

1. Bass synth on track 1, playing whatever bassline.
2. Compressor inserted on the bass track.
3. Kick drum sent to the compressor's sidechain input.
4. Threshold set so the compressor triggers heavily when the kick hits.
5. Attack very fast (0–5 ms).
6. Release medium (50–150 ms).

Every time the kick hits, the bass ducks 6–12 dB and quickly recovers. The result: kick and bass occupy their own moments rather than competing.

Surgical Sidechain Uses

Vocal duck. Sidechain the lead vocal to a compressor on a synth pad. Whenever the vocal is present, the pad ducks 2–3 dB, leaving room for the vocal without manual automation.

Reverb duck. Heavy reverb on a vocal, with the dry vocal sidechain-ducking the reverb. Reverb only swells in the gaps between phrases, not under the words.

Cleaning up low-end. Sidechain the bass to duck the kick. Yes, the reverse of the dance-music technique. Useful when you have a sustained bassline and want the kick's transient to cut through.

Multiband sidechain. A sidechain that only ducks specific frequencies. Useful for cleaning up vocal sibilance interfering with a hi-hat: sidechain the hat to duck only its 8 kHz region whenever the vocal "S" sounds occur.

Sidechain Tools Beyond Compressors

Many other processors accept sidechain input:

• Gates. Open the gate on track A whenever track B exceeds threshold.
• Filters. Modulate filter cutoff from a sidechained signal.
• De-essers. Use a brighter mic on the same source as the sidechain trigger.
• Modulation effects. Some chorus and phaser plugins respond to sidechain input.

Visual Sidechain (LFO Tool)

Some plugins (Xfer LFO Tool, Cableguys ShaperBox, Kilohearts Trance Gate) achieve the pumping effect without compression — they directly modulate volume according to a drawn shape, synced to the song tempo.

The advantage: predictable, repeatable shape, with no compression artefacts.

The disadvantage: sounds slightly less natural than a real compressor responding to a real kick.

For modern EDM, LFO Tool has become as common as sidechain compression itself.

Common Mistakes

Too much pumping in non-dance contexts. A heavy sidechain on a rock song's bass sounds gimmicky. Save the dramatic ducking for genres where it belongs.

Too fast a release. A release of 30 ms creates a "wub-wub" artefact. Set release long enough that the duck breathes naturally — usually 50–200 ms.

Sidechaining everything. If every track is ducking off the kick, you've made a compressor into a stylistic tic. Pick one or two elements that need it.

Forgetting the kick is doing the trigger work. If your sidechain stops working, check whether the kick is actually routed to the sidechain input — most "broken" sidechain setups are routing problems.

Recommendations

Further Reading

• Xfer LFO Tool Page
• Cableguys ShaperBox Page