Slightly mistuned voices perceptually fuse into one pitched tone

Evidence

Singers and violinists are never in perfect unison. Each has a slightly different pitch, which is drifting or oscillating (vibrato) slightly. The waveform cannot be perfectly periodic, even though it averages, say, 220 Hz in frequency. No law of physics dictates that we should hear a fused 220 Hz tone with a definite pitch in this circumstance, but we do. We hear a pleasant scintillation, but not individual singers, mistuned or not. This is the chorus effect. — Eric J. Heller, Why You Hear What You Hear- An…, 419

Categorization

• DEFINE: Defines the chorus effect: perceptual fusion of many slightly mistuned voices into a single scintillating tone.
• SEED: An essay angle on why ensembles sound ‘alive’ — the physics that makes a chorus more than the sum of its voices.