Sidechain
Techniques

What sidechain actually is

Every dynamics processor has two signal paths: the audio path (what you hear) and the detection path (what the processor listens to when deciding when and how much to act). By default both carry the same signal. Sidechain means routing something different into the detection path.

When the kick hits, its level crosses the threshold on the compressor sitting on the bass track. The compressor ducks the bass. The kick audio never touches the gain reduction stage: only its envelope does. That separation is the whole mechanism.

Classic compressor sidechain

A compressor on the target channel (bass, pad, synth) with its key input fed by the kick. Threshold and ratio control depth. Attack and release control shape.

DAW routing

Ableton Live:
  1. Add a Compressor to the bass track
  2. Click the "Sidechain" expander → enable
  3. Set Audio From → kick track (or a dedicated "SC Kick" track)
  4. Leave "Post FX" for most uses; "Pre FX" for a dry kick reference

Logic Pro:
  1. Add a Compressor to the bass channel strip
  2. Click the Sidechain dropdown (top right)
  3. Select the kick bus or aux send

FL Studio (Peak Controller method):
  1. On the bass mixer insert, right-click the volume knob → "Link to controller"
  2. Add a Peak Controller as the linked controller
  3. Set the Peak Controller source to the kick mixer insert
  4. Invert the response so kick peak = volume drop (Base: 100%, Volume: 0%)
  5. Attack and Release on the Peak Controller control duck shape

Pro Tools:
  1. On the bass track, insert a key input-capable compressor plugin
  2. Use a Key Input aux send from the kick track routed to the SC input
  3. Enable Key Input in the compressor

Switch between Compressor, LFO Tool, and Ghost MIDI, then adjust the sliders to see how the bass waveform and envelope change in real time. Compressor uses exponential curves; LFO Tool uses a smooth cosine shape: more symmetrical and perfectly consistent every hit.

Tuning the duck

Threshold and ratio: depth

Keep threshold low (−20 to −30 dBFS) so the compressor fires hard on every kick, regardless of kick dynamics. A high threshold means softer hits don't trigger the duck and your pumping becomes inconsistent.

Attack: instant vs. natural

0–2ms attack: tight, snappy pump. 5–15ms lets the kick transient through before the duck fully engages, so the kick punches harder because the bass is briefly still there under the initial click.

Release: the most musical parameter

Release is the breath of the pump. Sync it to tempo so the duck recovers just before the next kick fires.

Release timing formula:

  ms per beat  = 60000 / BPM
  ms per 16th  = 60000 / BPM / 4

  BPM   | beat  | 16th  | sweet spot release
  ------|-------|-------|-------------------
   90   | 667ms | 167ms | 500–580ms (slow, deep breath)
  120   | 500ms | 125ms | 380–450ms (classic house pump)
  128   | 469ms | 117ms | 350–420ms (techno, tight)
  140   | 429ms | 107ms | 300–380ms (fast techno / d&b)
  174   | 345ms |  86ms | 250–300ms (drum & bass)

  Rule: set release ≈ 0.75–0.85× the inter-kick interval
        so the duck fully recovers just before the next kick.
        If it's still ducking when the next kick arrives,
        the pumping gets chaotic — each cycle stacks on the last.

Genre release targets:

House (120 BPM):
  Attack:   1–3ms
  Release:  380–420ms
  Duck GR:  6–10 dB

Techno (130–140 BPM):
  Attack:   1–2ms
  Release:  280–340ms
  Duck GR:  4–8 dB

Drum & Bass (174 BPM):
  Attack:   2–5ms
  Release:  150–200ms
  Duck GR:  3–6 dB

Deep House (115 BPM):
  Attack:   3–8ms
  Release:  420–480ms
  Duck GR:  4–7 dB

LFO-based volume sidechaining

Kickstart and LFO Tool aren't compression. There's no detection circuit or threshold: a volume automation envelope is triggered rhythmically and applies a pre-defined curve directly to the signal. The duck is identical every hit regardless of what the kick is doing. Perfect consistency, zero dynamic response.

Ghost sidechain: the silent trigger

A muted MIDI track (short synth hits on the beat grid) feeds the sidechain input of the compressor on your bass. The fader is at −∞, so you never hear it. The bass ducks on the MIDI grid, not on the mix kick audio.

Ghost sidechain setup (Ableton):

  1. Create a new MIDI track
  2. Drop a simple synth (Operator, Analog) — short transient is ideal
  3. Draw MIDI notes on beats 1, 2, 3, 4
  4. Set this track's Volume to -inf (silent in mix)
  5. On the bass compressor:
     - Enable External Sidechain
     - Set "Audio From" → the ghost trigger track
  6. Adjust compressor settings as normal

  Shift MIDI notes slightly early for a pre-duck effect,
  or add an offset to delay the trigger.

Frequency-selective sidechain

A full-spectrum kick bus as sidechain source means everything in that bus triggers the duck: hat hits create micro-ducks, snare creates partial ducks. The bass sounds jittery. Fix it by filtering the detection signal, not the audio path.

HPF the sidechain key signal

Detection path filtering (Fabfilter Pro-C 2 / most modern compressors):

  HPF:  20 Hz  (remove sub rumble below kick)
  LPF:  150 Hz (remove everything above kick body)
  → Compressor now only responds to 20–150 Hz energy

  Hat bleeds, snare, percussion no longer trigger the duck.
  Only the kick sub and body fires the compressor.

  Ableton Compressor (no built-in SC EQ):
  → Add EQ Eight on the SC monitor path, or use a SC processing plugin

  Fabfilter Pro-C 2:
  → SC EQ is built-in, accessible directly in the SC section

Multiband sidechain: duck only the low end

Split the bass into two parallel bands. Put a sidechain compressor on the low band (20–200 Hz) only. The high band (200 Hz+) passes clean. The bass note stays present and audible; only the sub moves out of the kick's way. Standard practice in deep house and bass music.

Creative sidechain applications

Sidechain reverb

Put a sidechain compressor on a reverb return. Route the dry source into the sidechain input. The reverb ducks while the source plays, then swells back up in the gaps. Release is everything: for a vocal with 250ms gaps between words, 150–200ms release gives a natural breathing quality.

Pads and chords: rhythmic breath

Duck a sustained pad from the kick. Heavy depth (70–90%) with long release (400–450ms at 120 BPM) gives the dramatic progressive house swell. Light depth (20–35%) with medium release (200ms) creates groove you feel but don't consciously hear.

Whole-mix bus sidechain: the house pump

Put a compressor on the mix bus, sidechain it to the kick, and the entire mix ducks together on every hit, with pads, vocals, and percussion all breathing in sync. That rhythmic movement is essentially the signature sound of Daft Punk, Deadmau5, Disclosure.

Whole-mix bus sidechain:

  Compressor: on master bus or group bus
  Sidechain:  kick track (dedicated SC copy, not mix kick)
  Threshold:  -20 to -24 dBFS
  Ratio:       4:1 – 8:1
  Attack:      0–2ms
  Release:     380–450ms at 120 BPM
  Duck GR:     4–8 dB

  Note: exclude the kick from this bus or it will duck itself.
  Use a parallel kick send that bypasses the sidechained bus.

Envelope follower sidechain

An envelope follower extracts the amplitude envelope of one signal and uses it to modulate a parameter on something else, continuously and not just on a trigger. A filter on a pad that opens when the bass plays; a reverb send that grows when the lead gets quieter; a noise layer that swells on the kick. Use a follower plugin or DAW modulation matrix (Serum, Ableton rack routing).

When the pump should be heard

The pumping house sound is a deliberate aesthetic choice, not over-compression. When it works, it turns otherwise-static pads and strings into something rhythmically active.

Common mistakes

Release too long: cascading ducks

If release exceeds the interval between kicks, each new duck stacks on the tail of the last. Gain reduction builds across the bar and never recovers. At 120 BPM the inter-kick interval is 500ms. Keep release under 420ms.

Release too short: machine-gun chop

Very short release (20–50ms) with strong sidechain: the signal ducks hard and snaps straight back, creating a stutter. At extreme settings you get audible distortion from rapid gain changes. Unless the stutter is intentional, stay above 80ms.

Forgetting to HPF the sidechain key

Full-spectrum kick bus as sidechain source = every snare and hat creates its own duck. HPF at 80–150 Hz so only the kick fundamental fires the compressor.

Over-ducking or under-ducking

Over: 15 dB+ GR with fast attack and the bass disappears on every kick. Aim for 6–10 dB for intentional pumping; 3–5 dBfor clarity. Under: if you can't hear the effect, check the GR meter: the compressor may not be firing. Drop threshold until you see 6 dB+ on each hit.

Sidechaining from the mix bus

Using the master output as sidechain source means the compressor responds to everything: snare, claps, melodic transients. Use a dedicated pre-fader send from the kick, or a ghost track.

Cheat sheet

Method comparison

Attack and release by genre

Routing quick reference

Track: Bass
Plugin: Compressor
Sidechain: enable → Audio From → Kick
Post FX + Gain: 0 dB
Ratio: 4:1 · Threshold: -20 dBFS
Attack: 1-3ms · Release: 380-420ms

1. Bass mixer insert: right-click volume
2. Link to Controller → Peak Controller
3. Source: kick insert
4. Invert: Base 100%, Vol 0%
5. Attack/Release on Peak Controller

1. New MIDI track → simple synth
2. MIDI notes on beat grid
3. Track fader: -inf (silent)
4. Compressor/bass: SC → ghost track
5. Adjust compressor as normal

1. Bass track → send to two returns:
   - Return A: low band (20-200 Hz)
   - Return B: high band (200 Hz+)
2. Sidechain compressor on Return A only
3. Return B: bypass, no ducking
4. Blend returns back to master

1. Reverb on return track
2. Compressor after reverb on same return
3. SC input → dry source signal
4. Low threshold, moderate ratio
5. Release: matches gap between notes

1. Compressor on mix bus
2. SC → dedicated SC kick (pre-fader)
3. Ensure kick bypasses mix bus
4. Threshold: -22 dBFS · Ratio: 6:1
5. Attack: 1ms · Release: 400ms @ 120BPM
6. GR: 6-10 dB