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No. 127: Jan-Feb 2000

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Humans are born with one organ that is capable of astonishing performances that greatly exceed what is required for the tracking of animals and the grubbing of edible roots. This is the human brain, of course. Not as widely appreciated for its versatility is the human vocal tract. It can generate much more than brute grunts. It renders operatic arias of great beauty and frequency range. The vocal tract can do even more than that; it can carry two musical lines simultaneously. This skill is called "throat-singing" or "overtonesinging."

The best-known throat-singers live in the Tuva region of southern Siberia. The semi-nomadic herders of this wild region were evidently inspired to develop throat-singing so that they could better mimic the sounds they heard in nature: the singing of birds, the wind, the sounds of insects.

Throat-songs have two components. The first is at a low, sustained fundamental pitch, which can be likened to the drone of a bagpipe. The second, superimposed on the low drone, is a succession of flute-like sounds that resonates high above the drone. It is the second component that can be controlled so as to mirror natural sounds. The result is like nothing Mozart or Verdi conceived. But it is an art form valued in Tuva and a talent rather remarkable from a biologist's perspective.

One should compare the vocal tract to an organ pipe with its standing waves, except that the human pipe is only 7 inches long in the average adult male. One end of the human pipe is the mouth; the other is at the so-called "vocal folds" deep in the throat (larynx). To control their "instrument" throat-singers move their tongues back and forth to change the standing waves in the vocal tract. The source of raw sound is the vocal folds. It is the vocal tract that shapes the raw sound into musical tones. Biofeedback is also involved as the throatsingers tweak the rate and manner in which the vocal folds open and close.

(Levin, Theodore C., and Edgerton, Michael E.; "The Throat Singers of Tuva," Scientific American, 281:80, September 1999.)

Comments. The human throat is obviously a complex musical instrument, but what survival value does this remarkable instrument have? Did evolution overshoot its mark?

Incidentally, many birds can produce simultaneously two tones that are not harmonically related. However, these birds have a special doublebarreled organ called the syrinx. So, the avian "two-voice" phenomenon is not as unexpected as it is in humans. But, waxing skeptical, as usual, we ask why some birds would need a twovoice capability when ducks, herons, and many other birds survive very well with rather crude vocalizations.

From Science Frontiers #127, JAN-FEB 2000. � 1997 William R. Corliss