Gating

Gating an outside kick mic with one gate#

The microphone outside the kick drum has body and sounds great, but it is usually polluted with hi-hat, snare and cymbals. If you gate it directly, the bleed can give you ghost triggers. If you low-pass the key to get rid of the bleed, the gate opens too slowly, because the low end of a kick is slow, so you miss the transient. If you add look-ahead, the gating itself can start to sound odd. If you close the gate fast to keep the bleed out, you chop off the body.

You can get around this by keying the gate from the microphone inside the kick. It can sound plasticky and clicky on its own, so you don't even need to use it in the mix - you just use it as the side chain source for the gate for the outside kick.

Secondly you can split the gate by frequency: the highs open and close fast for the transient, while the lows are allowed to ring longer.

Gating the filter, not just the level#

You can go further and gate filter cutoff instead of gain. On each hit the filter opens, lets the transient through and closes again. The natural decay of the kick rings out and the bleed above it is mostly gone.

A high-pass gate does the same thing in the other direction, opening the low end on each hit, which clears kick rumble out of a snare mic. If you use both, you have a band-pass gate. This is a sound-design move for modern, heavily processed drums. It is not for classic rock, pop or jazz.

Keying from a cleaner source#

The same idea works across the kit. You can gate cymbal spill out of a tom mic by keying the gate from the tom's own resonant frequency. Whatever I am gating, I look for the part of the signal, or the other microphone, that only speaks when I want the gate to open, and key from that.