It is produced by the vibration of the ligamentous edges of the vocal cords, in whole or in part. Commonly cited in the context of singing, falsetto, a characteristic of phonation by both sexes, is also one of four main spoken vocal registers recognized by speech pathology.
The term falsetto is most often used in the context of singing to refer to a type of vocal phonation that enables the singer to sing notes beyond the vocal range of the normal or modal voice. The typical tone of falsetto register or M2, has usually a characteristic breathy and flute-like sound relatively free of overtones—which is more limited than its modal counterpart in both dynamic variation and tone quality. However, William Vennard points out that while most untrained people can sound comparatively "breathy" or "hooty" when using falsetto production, there are in rarer cases individuals who have developed a much stronger falsetto sound production which has more "ring" to it.
The modal voice, or modal register, and falsetto register differ primarily in the action of the vocal cords. Production of the normal voice involves vibration of the entire vocal cord, with the glottis opening first at the bottom and then at the top. Production of falsetto, on the other hand, vibrates only the ligamentous edges of the vocal folds while leaving each fold's body relatively relaxed. Transition from modal voice to falsetto occurs when each vocal cord's main body, or vocalis muscle, relaxes, enabling the cricothyroid muscles to stretch the vocal ligaments. William Vennard describes this process as follows:
With the vocalis muscles relaxed it is possible for the cricothyroids to place great longitudinal tension upon the vocal ligaments. The tension can be increased in order to raise the pitch even after the maximum length of the cords has been reached. This makes the vocal folds thin so that there is negligible vertical phase difference. The vocalis muscles fall to the sides of the larynx and the vibration take place almost entirely in the ligaments.
In the modal register, the vocal folds (when viewed with a stroboscope) are seen to contact with each other completely during each vibration, closing the gap between them fully, if just for a very short time. This closure cuts off the escaping air. When the air pressure in the trachea rises as a result of this closure, the folds are blown apart, while the vocal processes of the arytenoid cartilages remain in apposition. This creates an oval-shaped gap between the folds and some air escapes, lowering the pressure inside the trachea. Rhythmic repetition of this movement creates the note.