Sidechain
Using one signal to trigger a processor on another, most often a compressor
Related
Sidechain is a routing method: signal A is sent to the detector input of processor B, so A's level decides how much B processes signal C. The common case is sidechain compression: when the kick hits, the bass is pushed down to make room for the drum.
A compressor's sidechain input can come from a branch of the same track or from another track. Sidechain control can also drive a gate, filter or modulation, and filtering the sidechain signal lets only one frequency range trigger the ducking. Broadcast uses it to duck music under speech; mixing uses it to tidy up the low end.
The usual mistake is to equate sidechain with the obvious pumping heard in EDM. Pumping is simply how a compressor sounds under strong triggering; sidechain itself is a control path, and with gentle settings it can be an almost inaudible housekeeping tool.
Related → DAW
Sources
- 侧链压缩的检测路径与常见用法，参 Bobby Owsinski, The Mixing Engineer's Handbook 与通行混音教材；本文为原创表述
Used for fact-checking only; all prose is original.