Compression technique that ducks one signal in time with another — produces the characteristic "pumping" effect.
Definition
Sidechain compression is a production technique in which a compressor reduces the volume of one signal (the destination) in response to the level of another (the trigger). In trance, the most common use is sidechaining pads, basslines, and synth elements to the kick drum — every kick momentarily ducks the other elements, creating the characteristic "pumping" or "breathing" motion of modern dance music. Sidechaining serves two purposes: it carves frequency space for the kick to punch through cleanly, and it adds a rhythmic groove to otherwise sustained sounds. Heavy sidechaining is a signature of modern trance and progressive house production; subtle sidechaining is essential to almost every electronic mix. Plugins like Cableguys ShaperBox, Kickstart, and LFOTool make the effect easy to apply.