(Consider how muscles elsewhere in the body, such as those in our arms, begin to shake when strain or tension is prolonged. When this balance occurs, the antagonistic muscle systems develop an alternating pulse that is a reflection of the continued energy level required of them to maintain equilibrium and muscular health. Vibrato is the result of a balance between muscle systems in antagonistic relation to each other during phonation. It is generally assumed to result from neuromuscular excitation of the laryngeal mechanism. The parameters of vibrato include pitch excursion (oscillation), the temporal rate (cycles per second), and amplitude variance.Īlthough the purpose of vibrato is not completely understood, most voice scientists agree that vibrato enters vocal production as a relaxant principle because the body has a need for periodic muscle relaxation during heavy-duty or intense vocal activity, such as when singing sustained notes at high pitches. (It is more difficult to maintain exact pitch on a sustained note when singing in a 'straight tone'.) When vibrato is permitted to take free-swinging pitch excursion, it actually acts as a centering intonation device. The pitch variance remains centered around the actual written pitch, and the listener automatically hears the average of the pitches being sung. The effect is believed to add warmth to the voice.Īlthough vibrato is perceived as a pitch variant, it is discerned as a vocal timbre, or as an integral part of tone, evenly distributed over the group of notes, rather than as a pitch deviation. This periodic variation in the pitch (frequency) of a sustained musical note or tone should not exceed a semitone either way from the note itself. In vibrato, the voice is alternating subtly and very quickly between two pitches that are very close together.