Advanced sidechain processing

By making a dedicated channel for the sidechain, we can do almost any kind of processing to it Some compressors let you filter the sidechain signal (whether the internal or external one), most often to exclude bass frequencies from the compression response. We can actually go much further using the signal routing capabilities of modern DAWs. By isolating your sidechain signal on a separate channel, we can process it like any other channel in the project, adding processors that will – instead of being heard directly – influence the compressor’s behaviour to further refine the gain reduction we get. You can use this technique with an external signal or with the one you’re compressing, by sending the signal out first for processing, before it hits the compressor. If your DAW applies sidechaining using sends, do so with a pre-fade send, and bring down the fader so the affected signal isn’t heard via the mixer.

By high-pass filtering the sidechain signal, we can get the same effect as using the onboard EQ – useful if your compressor doesn’t have this function. We can also low-pass the signal to factor in the bass energy only, or draw any EQ curve we want.

adding a short delay to the sidechain signal. By doing this, the compressor will react later, like it would when reducing the Attack time. Or strip out the left or right channel of the sidechain, mono it, or add volume-shaping effects to alter the detected envelope.

Going further, try changing the dynamics of the sidechain signal before it feeds into the compressor. By compressing the sidechain, we’ll get a gentler compression response, letting the attacks through more; by expanding it, we’ll end up clamping down on transients more heavily.