You have several times told singers to allow a full-swinging vibrato. You told them it would happen if they didn't try to control the tone so much, or to hold back breath on long phrases. What do you mean by the term “full-swinging”?
Professional vocalism is characterized by a vibrato rate that is neither too narrow nor too wide in its pitch excursion. Sometimes singers, in the hope of avoiding oscillatory timbre (the dreaded wobble), are hesitant to let the full extent of pitch variance occur. They need to be reminded that full vibrancy, the source of normal vibrato, cannot result if pitch variation is restricted. Fiberoptic studies reveal that not only the vocal folds oscillate during vibrato; motion takes place in the pharyngeal wall, the epiglottis, and, to some extent, the base of the tongue. This motion is a major component of the relaxation process that comes from coordinating breath energy with vocal-fold responses, and is essential to professional vocalism. Vibrato is generally assumed to result from neuromuscular excitation of the laryngeal mechanism; yet despite frequent subjection to analysis, the precise source of the phenomenon of vibrato remains elusive. Vibrato lies in the necessity