When recording one source with two or more microphones one of the most important factors to watch out for is phase correlation between the microphones. If the microphones are out of phase with each other the sound waves will begin to cancel and the result will manifest audibly as what can be referred to as a comb filtering effect.
In this tutorial from Create Music Productions, Corey explains how to setup a scenario to train your ears to recognize different variants of a comb filter effect. Maintaining phase correlation will prove useful when stereo micing acoustic and electric instruments, live drum kits and ensembles.













