Mono Compatibility

Many playback situations collapse stereo to mono — club and PA systems, phone speakers, some Bluetooth speakers, and distant listening in a large room. When the left and right channels are summed, any content that is out of phase between them partially or fully cancels, so a wide, phasey sound can shrink or vanish in mono. Checking mono compatibility means auditioning your mix summed to mono and listening for elements that lose level, especially the bass and anything widened with stereo effects. Keeping low frequencies centered, using stereo widening in moderation, and watching a correlation meter all help. A mix that survives the mono test sounds solid everywhere, while one that leans on phase tricks can fall apart on real systems.