I have heard on a couple occasions of engineers using one instrument to trigger a sound generated from another electronically. For example, a gate would be "attached" to a kick drum, a synth holding a very low note (40 or 50 Hz) would be triggered when the kick gate would open giving a "sub" note to the mix whenever it is struck. I understand the theory, I just am not sure how to "wire" that sort of a setup. I'm guessing you would need a gate that has two channels plus the capability of "coupling" so that the gate opened by the input on channel A would also open the gate on channel B (assuming the input on channel B wasn't loud enough to open the gate on it's own). Can somebody clarify the practical application of this method? Thanks!