What is “Sidechaining?”
This is short for “compressing a sound using a different sound as the trigger or key for the compressor.” Really rolls of the tongue.
Used subtly it’s an effective way to “glue” bass with drums, or push reverb behind vocals or countless other uses. Used aggressively, like in this example you get rhythmic pumping effects.
Watch this video for more on setting up sidechain effects.
In EDM Production the synths are often sidechain compressed by the kick drum. But there are times when the kick drops out and you want the pumping effect to remain. The Ghost Sidechain Trigger (as shown in this video) is simply a duplicate of the main kick, but it is not sent to the main output and is not heard.
Taking this concept further, you could create different patterns for your ghost trigger, using short and long pulses, different intensities. Really anything is possible with this.