You may have noticed that Live’s Compressor sometimes produces an audible clicking sound in the signal when the sidechain is activated.
There are two easy ways around this.
Turn up the Knee:
This applies the compression more gradually and often stops the clicking.
Or, switch Mode to FF1:
FF1 tends to be the most lo-fi mode of Compressor and is often used when you want a more obvious compression effect. With the sidechain activated, it can produce surprisingly great sounding results with lots of punch.