Mono is audio with a single channel — one waveform reproduced identically on every speaker. It is the natural choice for anything centered on a single source: dialogue, voice-over, podcasts, and the vast majority of real-time voice calls, where one microphone captures one speaker. Mono is also bandwidth-cheap, which matters in WebRTC and telephony. Its quiet virtue is robustness: a mono mix has no phase relationship to collapse, so it survives summing, downmixing, and poor playback unchanged. Checking that a stereo or surround mix still sounds right when folded to mono — 'mono compatibility' — is a standard broadcast quality gate.
