What is Sidechaining? A Comprehensive Guide for Music Producers

Ever wondered how, when a radio DJ speaks over some background music, the music “ducks” or decreases in volume exactly when he/she speaks, and goes back to the normal volume the moment the DJ stops speaking? This is called the sidechain effect. Whenever the DJ speaks, a compressor is activated upon the background music. This causes the music to drop way down so it doesn’t interrupt the DJ’s speech. When he’s done talking, the silence on his track deactivates the compressor on the background music and it once again becomes louder in the mix. This technique is also used to cause background sound to drop during the voice narration in a documentary film.

Sidechaining is often also used in music production: one sound or instrument in a song is used as a trigger to cause another sound or instrument to “duck”. For example, if you want the bass volume to momentarily drop when the kick drum plays, sidechaining can help you achieve that. It would help the kick drum “punch through” clearer, emphasising the pulse of the song. If the two sounds are not separated, the overall sound can get muddy, as the low frequencies in the bass and the kick drum would clash with each other, distorting the sound. Sidechaining is one of the ways that different sounds can be separated and taken out of each other’s way momentarily.

This technique is often used in electronic dance music. It creates a distinctive sound sometimes described as “pumping”. The threshold of a sidechain can be adjusted to make it pump gently or aggressively. When the sidechain compression is heavy enough, it can make the bass go “WUB WUB” as it ducks completely and quickly comes back. Although most commonly used with compressors, sidechaining can be used with other effects as well, like EQ or gate. Applying the sidechain of a gate would have the opposite effect: it would trigger the bass to play exactly when the kick plays. With an EQ, it could be used to momentarily suppress a particular range of frequencies of the bass (or any other instrument) whenever the kick plays.