12. Sidechain — the “pumping” trick

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In a lot of dance music you can hear the whole track briefly “breathe” or “pump” in time with the kick drum. The trick: every time the kick hits, the other sounds are turned down for a split second, then swell back up. This makes room for the kick to punch through cleanly instead of fighting the bass and pads.

In .track you get this with the duck parameter on a voice. Set duck (0–1) on a pad or bass, and it dips every time the kick row fires, swelling back over about 120 ms:

steps 16
scale A minor

inst pad = preset choir duck 0.7

kick x...x...x...x...
pad  1+3+5 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

The pad holds one long chord, but you hear it pump — hard on each kick, full in between.

Once you notice it, you’ll hear it in countless songs — that rhythmic “in-out” breathing under the beat.

Real name: sidechain compression / ducking.

✅ Live now: duck 0–1 on any voice is real. The duck source is fixed — it always follows the row literally named kick — so name your kick row kick and add duck to whatever should breathe with it. Turn it toward 1 for a hard pump, 0 to switch it off.

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