The human instrument.

Januar y 20 0 8 The human vocal system would not receive much acclaim if instrument makers placed it in a lineup of traditional orchestral instruments. Arranged by size, for example, the voice box (larynx)—and the airway it sits in—would be grouped with the piccolo, among the smallest of mechanical music makers. And yet experienced singers compete well with all man-made instruments, one on one and even paired with full orchestras. Recent investigations of how our singing voice generates a remarkable range of sounds have revealed surprising complexity in the behavior of the vocal system’s elements and in the ways they interact. For more than half a century, scientists explained the voice’s ability to create song by invoking a so-called linear theory of speech acoustics, whereby the source of sound and the resonator of sound (or amplifier) work independently [see “The Acoustics of the Singing Voice,” by Johan Sundberg; Scientific American, March 1977]. Researchers have now learned, however, that nonlinear interactions—those in which source and resonator feed off each other—play an unexpectedly crucial role in generating human sound. Such insights now make it possible to describe how great singers produce those amazing sounds.