A polarity-inverted parallel gate channel can implement sidechain ducking without a dedicated ducker plugin

When a sidechain ducker is unavailable, the same effect can be achieved using a gate: (1) send the signal to be ducked to a gate as a send effect; (2) key the gate’s sidechain from the signal that should trigger ducking (e.g., lead vocal); (3) invert the polarity of the gate’s output; (4) blend the inverted output into the mix at the desired depth. When the trigger signal (vocal) is present, the gate opens, allowing through the inverted signal, which phase-cancels the main signal—ducking it. Adjusting the send level to the gate controls the depth of the ducking effect.

Examples

Guitar bus ducking under vocal: send guitars to a gate (keyed from vocal), invert the gate return polarity, and blend at -6 dB into the mix. Whenever the vocal plays, the guitars drop by the cancel amount.

Assessment

Describe the polarity-inversion gate trick for ducking without a dedicated ducker. Explain what determines the depth of ducking in this setup.