Was about to use this technique, and thought it was worth sharing.
Some folks give better vocal performances when they are just singing along with the speakers rather than using headphones. But then you end up with leakage from the rough mix. However there is a way to minimize the leakage to almost inaudible levels.
- Set your mix to mono and pan it to come from one and not two monitor speakers.
- Use a directional microphone on the vocalist and situate it so it points a null node to the speaker to minimize the leakage you actually record.
- Record as many vocal takes as needed.
- After the vocalist is done, record a new track with the vocalist staying in the same position as they were when they were singing. The purpose of this track is to record just the leakage you get from the rough mix into the mic. You keep the vocalist in place and don’t move or change any levels so you get as close to capturing exactly the leakage that occurred during the tracking.
- Take this leakage track and reverse the phase on it.
- For each vocal take, mix it and the phased reversed leakage track together.
- Adjust the level of the phased reversed leakage track in the mix until the backing level is minimized.
FYI, noise canceling headphones work on the same principle of summing together noise and phase reversed noise.