Tuvan overtone singers merge formants to amplify single harmonics into a distinct second melody

Evidence

A singer’s effort to correctly shape the vocal tract can dramatically enhance power in certain frequency ranges, increasing total power by source loading and altering timbre. This art reaches a pinnacle in Tuvan singing, where the merging of formants to form a sharp resonance peak strongly enhances a partial of the vocal fold source, provided the resonance is tuned to the vocal overtone or vice versa (figure 17.10). When it is, a pure sinusoidal frequency sings loudly above the other frequencies present. Two tunes can be sung at once. The first tune is sung in a low pitch, which creates many partials of much higher frequency. Normally these are weak, but the formant tuning resonance is adjusted to play another tune ranging over selected overtones of each voiced note. — Eric J. Heller, Why You Hear What You Hear- An…, 1692

Categorization

• XREF: Connects to formant theory from earlier voice chapters and to chapter 23’s pitch perception material; also ties to the natural trumpet’s overtone discussion.
• ADDENDUM: Relates to ‘Grafting & Growth’ only loosely (not really); but the pseudo-multiphonics distinction is a concrete mechanism example useful for the reader’s why-do-we-hear-what-we-hear question.
• SEED: An essay on how the human voice is a physical instrument whose geometry we tune live — Tuvan singing as the extreme case.