Mean frequency of vocal vibrato relative to target frequency

Six professional singers of early and contemporary music produced sustained vowel phonations at three pitch levels beginning with straight tone leading to either vibrato or to vibrato followed by exaggerated vibrato. Mean fundamental frequency (F 0) during the two vibrato conditions was compared with the target F 0, which was measured during straight tone production. During usual vibrato production the preponderance of singers lowered their mean F 0, and a lesser number maintained the straight tone mean. Only one subject elevated mean vibrato F 0. During exaggerated vibrato phonation, there were four instances of elevated F 0, but the same number of lowered F 0 as for usual vibrato.