The Record Producer
Page 70
Chapter 5
The all encompassing reality of wave relationships.
Microphone phasing only occurs between microphones that vary
slightly in distance from the instrument they are recording (Distance
variances too slight to be detected visually). Only their
corresponding channels need to be messed with.

When the phase is reversed on one of two signals that are 90
degrees out of phase, the resulting signals will still be 90 degrees
out of phase.

Visualization: 2 signals 90 degrees out of phase...
Visualization: 2 signals STILL 90 degrees out of phase...