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The Physics Behind Overtone Singing

Overtone Singing is a vocal technique used by singers which creates the perception of singing more than one pitch simultaneously. The technique has been used across many cultures and continents, from Asia to Europe to Africa. Despite being an ancient technique, overtone singing makes use of physics that were only understood much later.

Overtones

Musical sounds are often generated from a source, such as a string or block, that emits a series of frequencies when vibrating. The lowest frequency is referred to in music as the fundamental frequency while the following frequencies are reffered to as the overtones. While the brain tends to perceive the fundamental frequency alone, sound waves according to the overtone frequencies are also emitted at varying levels of power.

While the human brain perceives the fundamental frequency and does not naturally distinguish it from its overtones, changes in the emphasis of different overtones create a perceivable change in tone. In music, this tonal quality is often referred to as the timbre, and allows human brains to distinguish between the sounds of different instruments, voices, and other mediums. For vocalists, different syllables and timbres are created through the movement and adjustment of the vocal system, including the vocal folds, jaw movement, tongue movement, etc.

Overtone singing gives the perception through vocal technique of one of the overtones of a sung fundamental frequency being distinctively heard as well by the human ear. Vocalists who use this technique are also able to give the perception of the movement of the higher frequency to other overtone frequencies, while simultaneously maintaining the fundamental frequency.