Although the human vocal system is small, it manages to create sounds as varied and beautiful as those produced by a variety of musical instruments. The question is: How can singers produce all those remarkable sounds?

All instruments, including our singing voices, have a sound source, a resonator that reinforces (amplifies) the basic sound and a radiator that transmits the sound to listeners. In people, the source is vibrating vocal folds (vocal cords) of the larynx or voice box; the resonator is the sound-boosting airway above the larynx; and the radiator is the opening of the mouth.

The human voice can create an impressive array of sounds because it relies on non-linear feedback by which a small input can result in a disproportionately large output. One of the voice’s more effective nonlinear mechanisms is inertive reactance, whereby singers create special conditions in their vocal tract to amplify sounds generated by the vocal folds.