Eighty singers and a duet are perceived as the same pitch

Evidence

We usually take our cues for pitch from the first few prominent peaks in the autocorrelation, as we shall discuss at length in chapter 23. The first part of both autocorrelations, 80 singers and 2, is very similar—almost identical, in fact. Thus if autocorrelation peaks are indeed the key to pitch perception, the chorus and the duet must be judged to have the same pitch. — Eric J. Heller, Why You Hear What You Hear- An…, 423

Categorization

• XREF: Preview of chapter 23’s pitch-perception model; supports the thesis that early autocorrelation peaks drive pitch.
• QUESTION: This claims perceptual pitch equivalence despite vastly different timbre richness — how does the model hold across chorus-to-duet extremes?