In Tuvan throat singing, dual tones are produced simultaneously. The unique style of singing originated in central Asia, where Tuvans have been practicing for generations.
Birds and some frogs can produce two distinct tones, but the Russian republic of Tuva, located in central Asia, is one of only a few locations where throat singing is practiced by humans.ย
"The question becomes, why are there two pitches heard when Tuvan singers sing? They don't have two sets of vocal cords," Narayan said.
In humans, vocal folds make sound by vibrating creating a buzzing noise. How fast or slow the vocal cords vibrate determines whether a high- or low-pitched sound is produced. The faster they vibrate, the higher the pitch of the voice. But they also produce a series of harmonics or "overtones." The mouth and tongue shape theses overtones, creating resonances at certain frequencies called formants. Vowels in human speech are determined by the first three formants - F1, F2 and F3.
Each formant is usually distinct, but Tuvan singers can merge multiple formants to create one exceedingly sharpened formant.
"The Tuvans are able to make this sound through such precise control of their vocal track that they can kind of tease these things out and create simultaneously sounds. One of the things that's so remarkable about it is that it doesn't sound like any human could do this, to have that degree of motor control," Bergevin said.
"Potentially anyone could learn to do this," Story said, "but it takes a lot of practice."
Reference: "Overtone focusing in biphonic tuvan throat singing" by Christopher Bergevin, Chandan Narayan, Joy Williams, Natasha Mhatre, Jennifer KE Steeves, Joshua GW Bernstein and Brad Story, 12 February 2020, eLife.
DOI: 10.7554/eLife.50476