Two capsules may be combined into a single housing so that one mic can capture
both left and right sides of the sound field.
This is much more convenient than setting two mics on a stereo bar, but obviously
Some stereo mics use the MS principle where one cardioid capsule (M) captures
the full width of the sound stage while the other figure-of-eight capsule (S)
captures the side-to-side differences.
The MS output can be processed to give conventional left and right signals.