Isotonic vocalis contraction as a means of producing rapid decreases in Fo

In a first experiment, subjects were presented with frequency modulated tones and instructed to vary their own vocal pitch to match what they were hearing. It was found that the faster a subject modulated his voice, the higher the carrier frequency he produced became relative to that specified as his target. In a second experiment, subjects were presented with one or two target tones. After one was presented, they were required to reproduce its pitch with their own voice. They did so accurately. After two were presented, they were asked to oscillate the pitch of their voice as rapidly as possible between them. In this case, it was found that the tones which were produced were higher than those specified by the targets. It is argued that the results from both experiments indicate that fast decreases in voice pitch are produced by isotonic contraction of the vocalis muscles.