Side-Chain (or just sidechain) is a very popular mixing technique that basically lets you control an FX with an external signal that is being applied to another signal.
In this tutorial I am demonstrating one of the most common mixing tricks: a sidechained noise gate! A gate is the simple dynamic processor that controls the output of an audio channel. When the incoming signal’s amplitude is below the gate’s threshold then the gate “blocks” the sound, meaning there will be no audio output. When the amplitude is above the threshold the gate opens and the signal can pass through. Sidechaining a gate means that the closing or opening of the gate depends on another channel’s signal. Thus sidechaining a gate can be used to trigger the output of different channels.
In this video I send the output of the kickdrum channel to the input of the keyboards’ gate. In that way every kickdrum hit triggers the sound of keyboards. Use your imagination and use this technique in different situations to create rhythmically interesting connections.
https://www.youtube.com/watch?v=fNdni4Vaegk&feature=youtu.be