A sidechain is a secondary input to a compressor which triggers increased compression. The most common example is a kick drum sidechaining a pad. When the kick hits, the pad sound will be compressed more and "duck" behind the kick. A little bit of side-chaining can be used to make some sounds seem louder and stand out in a mix, while a lot of sidechain can be used as an effect on its own, like the "pumping white noise" effect found in a lot of EDM songs.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence