Assessment of Register Accessibility and Vocal Range Using Electroglottography Analysis in Experienced Singers

Classical pedagogy often classifies vocal registers based on pitch range, assigning low notes to chest voice (M1) and high notes to head voice (M2). Recent evidence indicates that trained singers can access both registers across a wider pitch spectrum than traditionally recognized. This exploratory study examined register accessibility and boundaries in relation to historical literature, the ability of electroglottographic (EGG) closed quotient (CQ) to distinguish between registers, and singers' preconceived notions about register use and mixed voice.

After determining 10 professionally trained singers' phonatable singing ranges (five male, five female), the participants completed three tasks: (1) producing sex-specific low and high target pitches in M1 and M2, (2) phonating their lowest pitch in each register, and (3) phonating their highest pitch in each register. A questionnaire assessed singing background and perceptions of range accessibility. Perceptual register classifications by expert raters were compared with CQ-based predictions. Statistical analyses included paired t tests to compare register and total ranges; repeated-measures analysis of variances to assess CQ across pitch, register, and sex; and logistic regressions to evaluate CQ as a predictor of register and training years as a predictor of extreme-range success.

Eight singers achieved their lowest pitch in M2, while only three reached their highest pitch in M1. Nine of ten singers produced both high and low target pitches in M1; all produced both target pitches in M2. CQ was significantly higher in M1 than M2 during the target register task, with a sex effect observed in the target task, but not during the extreme ranges task. There was a significant effect of register on CQ for both target tasks and at extreme ranges. Logistic regression demonstrated that CQ significantly predicted register classification. Questionnaire responses varied, with some aligning and others diverging from measured accessibility.

Highly trained singers can extend register use beyond traditional pitch-based boundaries, especially downward into M2. CQ effectively distinguishes between registers, whereas self-reported perceptions do not always align with measurable capability. These findings support more flexible teaching approaches to register use, emphasizing proprioceptive awareness, coordinated laryngeal musculature, and freedom in register choices.