How many distinct musical pitches is it possible for the human voice to carry at one time? If two or more are possible, can you explain how the vocal folds are able to carry different vibration patterns simultaneously?
Voice is produced in the larynx as air passes through a space between the vocal folds. The tension in the folds determines their rate of vibration, and that determines pitch. Since there are two folds, two pitches are possible. Normally, of course, the folds are stretched to the same tension, but it’s not uncommon for a growth or obstruction on one of the folds to cause it to vibrate at a different rate than its partner. The result is the voicing of two different pitches simultaneously.
Apparently–and here we get to the interesting part–it’s also possible for some people to control their vocal folds to sing two pitches intentionally. A paper presented a few years ago to a national association of ear, nose, and throat doctors (or otolaryngologists, for the more pretentiously inclined) documented the case of a girl who could control the length of her vocal folds to the extent that she could sing with herself in thirds (do-mi, in first-grade musical parlance). Her sister was capable of a similar stunt.
I can’t tell you exactly how she did this, since not even the doctors are sure, but I can tell you it wasn’t considered a pathological case–in other words, the ability wasn’t due to any gross physical deformity. All I know is I would have paid good money to hear her perform.
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