The H4n provides two different ways of recording great-sounding stereo. The X/Y technique is an excellent way to cover a wide area while still capturing sound sources in the center with clarity and definition, making it ideal for all types of live stereo recording.
The H4n's built-in X/Y microphone provides two matched unidirectional microphones. The angle of the two can easily be changed from 90 degrees for a tightly focused stereo image to 120 degrees for a wider image. (US Patent 8184815)
The H4n also provides an onboard MS decoder so you can do MS ("Mid-Side") recording using external microphones. This is an incredible technique that allows you to adjust the width of the stereo image after it has been recorded, while maintaining perfect mono compatibility, making it especially useful for film, video and television projects.
Adjustable Stereo X/Y Microphone Can Record 4 Tracks Simultaneously 2 x XLR / 1/4" Combination Input Jacks 3.5mm Line Input with 2.5V Plug-In Power 28 & 48V Phantom Power Record & Play WAV & MP3 Formats AD/DA Conversion up to 24-Bit / 96 kHz Built-In Metronome and Chromatic Tuner 2-In/2-Out Interface via USB Rubberized Body with Locking XLR Jacks