The Invisible Sidechain: The Final 10% That Gels Your Mix Together
This is the bit between mixing and mastering. Your mix is done, you are happy with it, and it still sounds a little loose. Everything is sitting in its own spot but it does not quite move as one thing. This technique fixes that, and it is subtle enough that nobody will ever hear it working. That is why it is called the invisible sidechain.
The idea
Every mix has focus points. Usually the kick, the vocal and the snare (or clap). They are the things driving the track, so they need to stay solid, centred and out front. Everything else is a supporting act.
The invisible sidechain splits the whole track into three frequency bands and lets each focus point very gently push the rest of its band out of the way:
- Lows are driven by the kick
- Mids are driven by the vocal
- Highs are driven by the snare or clap
Normal sidechaining pulls the bass 6dB out of the way of the kick. This is nothing like that. We are talking 1 or 2dB, spread across loads of things, just enough to get the track breathing together.
Set up three buses
Make three buses: low sidechain, mid sidechain and high sidechain. Put FabFilter Pro-MB on each one, set up as three bands. The preset is called Streaky Side Chain Bus and you can grab it from the download at the top of this page.
Same preset, same plugin on all three buses. The only thing that changes is which band is switched on:
- Low bus: only the low band on, crossover around 200Hz, sidechained from the kick
- Mid bus: only the mid band on, sidechained from the vocal
- High bus: only the high band on, crossover around 5kHz, sidechained from the snare or clap
On every band: fast attack, fast release, range set to about -2dB. Play the track and adjust until you are only seeing 1 or 2dB of gain reduction.
Route everything to the right bus
The kick, vocal and snare go straight to the stereo out. They are the focus points, so they never go through a sidechain bus. You want them solid and still.
Then go through the rest of your instruments and ask what band each one lives in:
- Low bus: bass, and anything percussive with low end in it. A bongo loop went here so the kick gives it a bit of groove.
- Mid bus: synths, and all your vocal reverbs and delays. Having the effects duck from the vocal is a big part of why the vocal comes forward.
- High bus: hats, cymbals, anything bright and busy, so the snare bites through.
One extra move: copy the kick sidechain onto the mid bus as well. The mid-range stuff is then being pushed by the kick and the vocal, which gives the kick even more drive without touching its level.
Most percussion can be left alone. You do not want to sidechain everything, just the things that are getting in the way of a focus point.
How to hear it working
Flick it in and out while listening to the vocal. With it on, everything pulls together and the kick, vocal and snare sit right out front. With it off, the mix sounds a bit individual and loose. That is the whole trick. Nothing jumps out, it just feels finished.
