Sidechain: ducking, trigger, EQ and gate in sidechain

What it is and how it works

In sidechaining, the detector of a dynamics processor listens to a signal different from the one it processes. The most common case is ducking: the bass (or the pad, or the whole music bus) dips when the kick plays, so the kick comes through freely and the groove “breathes”. The same principle applies to a vocal that lowers guitars or reverbs, a kick that opens a gate on a noise, a vocal that drives a dynamic EQ on the music.

Three ways to do it

1. Compressor in sidechain: reacts to the real level of the trigger (more natural, follows the dynamics).
2. Volume shaper (a curve drawn and repeated in time: Kickstart 2, LFOTool, Cableguys VolumeShaper/ShaperBox, Duck; in FL Gross Beat or an automation / Fruity Peak Controller): exact shape, always the same, no dependence on level. Standard in EDM and future bass.
3. Dynamic EQ in sidechain: lowers only the conflicting band (e.g. the bass's 50–90 Hz when the kick plays), the rest of the bass stays intact. More transparent.

How to do it in FL Studio (compressor)

1. Select the mixer track of the kick (source).
2. On the bass track (destination), right-click the route arrow → “Sidechain to this track”. The link carries the signal to the detector but doesn't add the kick's audio to the bass.
3. On the bass insert Fruity Limiter (COMP tab) or Fruity Compressor and choose the kick's track number in the SIDECHAIN selector.
4. Set threshold, ratio, attack, release (see table).
5. Ghost trigger: if you don't want the audible kick to be the driver (kick with variable tails, or you want ducking even where the kick doesn't play), create a channel with a short kick, route it to a mixer track that doesn't go to the Master (remove the route to the Master) and use it only as the sidechain source.

Alternatives: Fruity Peak Controller on the kick and link its output to the bass's volume (Link to controller, inverted curve); Transmitter (separates transient and sustain, has a sidechain input and sidechain outputs to drive other processors); LuxeVerb with the Envelope at negative scale for reverb ducking.

Parameters and typical values

• Threshold: low enough to get the desired reduction on every hit.
• Ratio: 4:1–∞:1 for obvious ducking; 2–3:1 for discreet ducking.
• Attack: 0–1 ms (the bass must dip immediately); 3–10 ms if you want to leave a bit of the bass's attack.
• Hold: 0–30 ms if available.
• Release: decides the shape of the breathing. Tie it to the tempo: at 124 BPM 1/8 ≈ 242 ms, 1/16 ≈ 121 ms. House bass: 80–150 ms; pad/music bus in EDM: 150–300 ms (obvious pumping); trap 808: 30–80 ms (only to free up the kick's attack).
• GR / depth: discreet 2–4 dB; obvious 6–12 dB; EDM “pumping” down to −∞ with a shaper.
• Lookahead: 1–5 ms if the compressor offers it (the bass dips a moment before the kick).

Starting settings

Advanced uses

• Reverb sidechained to the vocal: the reverb dips while the vocal sings and opens up in the pauses; clear vocal but big space.
• Delay ducking: the repeats come out only between phrases.
• Trance gate in sidechain: a hi-hat pattern or a ghost track opens a gate on a pad (rhythm out of nothing).
• Multiband sidechain: only the lows of the music bus dip with the kick (Maximus or multiband with sidechain, Pro-MB).
• Cross sidechain: kick → bass and bass → (light) kick, no; better to decide who is in charge.

By genre

• House, techno, EDM: a compositional element; bass and pads pump in time.
• Future bass: extreme pumping on supersaw chords (shaper, −∞ dB, release 1/4).
• Trap/drill: light ducking or dynamic EQ; the 808 is often written so as not to overlap with the kick.
• Pop: discreet ducking (2–3 dB) on pads and synth basses; vocal → reverb sidechain.
• Rock: rare; sometimes vocal → guitars with dynamic EQ.

Common mistakes

• Release too long: the bass doesn't come back up before the next kick, a “dragging” groove and weak bass.
• Attack too slow: click or double kick+bass attack.
• Huge ducking even where it isn't needed (intimate verses): automate the depth.
• Using the audible kick as the trigger when it has long tails or variable volumes: the ducking changes from hit to hit (use a ghost trigger).
• Forgetting latency: plugins with lookahead on the trigger and not on the destination misalign; FL compensates for latency, but check alignment with the oscilloscope.

How to hear it

• Solo bass and kick: the bass should “inhale” on the kick and come back full before the next hit.
• Exaggerate to −15 dB, set the release in time, then reduce the depth until the groove remains but the ducking doesn't disturb.