Overtone Singing

When a Tuvan or Mongolian throat singer performs khoomei, a listener can hear what sounds like two distinct pitches coming from a single voice at once: a low, steady drone and, floating above it, a clear, almost flute-like whistling tone. It can sound as though the singer produces two separate notes at once, though the mechanism works differently. Every human voice, in ordinary speech or singing, naturally produces not just one pitch but an entire spectrum of overtones, or harmonics, layered on top of that fundamental pitch. Under normal conditions, these overtones blend together and are not perceived as separate sounds. Overtone singers have trained precise control over the shape of their vocal tract, adjusting tongue position and the shape of the mouth and throat, to act as a filter that dramatically amplifies one harmonic already present in the voice while suppressing the others around it. The result is not a second pitch created from nothing, but one existing harmonic made audible on its own. Ethnomusicologists have documented khoomei's long association with herding cultures of the open steppe, and voice scientists now use spectrograms to visualize exactly which harmonic a singer has amplified. The technique demonstrates that ordinary voices already contain a far richer harmonic structure than casual listening typically reveals.