Cricothyroid muscle and thyroarytenoid muscle dominance in vocal register control: preliminary results.

HYPOTHESIS: Headmix and head registers use cricothyroid (CT) muscle dominant voicing, whereas chest and chestmix registers use thyroarytenoid (TA) muscle dominant voicing. STUDY DESIGN: Cross-sectional study. METHODS: CT and TA electromyographic data obtained from five untrained singers and two trained singers were analyzed to determine CT and TA muscle dominance as a function of register. Simultaneous recordings of TA and CT muscle activity and audio were obtained during production of pitch glides and a variety of midrange and upper pitches in chest, chestmix, headmix, and head registers. RESULTS: TA dominant phonation was only observed for chest productions and headmix/head register productions below 300 Hz. All phonation above 300 Hz, regardless of register, showed CT:TA muscle activity ratios that were CT dominant or close to 1, indicating nearly equal CT and TA muscle activity. This was true for all subjects on all vocal tasks. For the subjects sampled in this study, pitch level appeared to have a greater effect on TA and CT muscle dominance than vocal register. CONCLUSION: Preliminary findings regarding CT and TA dominance and register control do not support the assumption that all chest and chestmix production has greater TA muscle activity than CT muscle activity or that all headmix and head production require greater CT muscle activity than TA muscle activity. The data indicate that pitch level may play a greater role in determining TA and CT dominance than register.

Laryngeal muscle activity and vocal fold adduction during chest, chestmix, headmix, and head registers in females.

HYPOTHESIS: Commercial singers produce chestmix register by maintaining or increasing adduction of the vocal processes (VPs) and by engaging the thyroarytenoid (TA) muscle to a greater degree than they would to produce head register. STUDY DESIGN: Prospective cohort study. METHODS: Simultaneous recordings of TA and cricothyroid (CT) muscle activity, videonasendoscopy, and audio were obtained from seven female singers during production of a variety of midrange pitches in chest, chestmix, headmix, and head registers. Fast Fourier transforms were performed to measure the energy in the fundamental frequency and in mid and upper frequency harmonics to determine if the productions that were judged as perceptually distinct registers also showed distinctive acoustic characteristics. Then, measures of TA and CT muscle activity and vocal fold adduction ratings were obtained to determine how these varied as a function of pitch and register. RESULTS: Spectral tilt increased as subjects shifted from chest to chestmix to headmix and finally into head register. For same pitch phonation, subjects increased TA muscle activity and vocal fold adduction as they shifted register from head to headmix to chestmix to chest, particularly during production of higher frequencies. CT activity appeared to be more related to pitch rather than register control. CONCLUSION: Nonclassically trained singers were able to produce pitches at the high end of the midrange in chestmix register by increasing TA muscle activity and adduction of the VPs.