Effects of Intentional Register Instability During Onset of High-Intensity Phonation

This study investigated the effects of the "crack-sob" onset-a distinctive vocal technique combining a sob gesture with an intentional pitch break-on vocal fold function during high-intensity singing. We hypothesized that this onset would either decrease glottal adduction and increase vocal fold vibration stability or alternatively, show no measurable effects while still providing perceived benefits to singers.

Prospective observational cohort study.

Twenty professional musical theatre singers (10 male, 10 female) performed high-intensity sustained notes with and without the crack-sob onset using both a control phrase and self-selected repertoire. Electroglottography measured contact quotient (CQ) and its relative standard deviation (relSDCQ). Acoustic analysis quantified smoothed cepstral peak prominence (CPPS), harmonics-to-noise ratio (HNR), and vocal intensity (dB SPL). Linear mixed effects modeling was used to analyze the effects of the crack-sob maneuver, with sex and vocal phrase as covariates.

The crack-sob onset showed no significant effects on any measured parameters. CQ remained consistent at 66% regardless of onset type. No significant changes were observed in CPPS, dB SPL, relSDCQ, or HNR when using the crack-sob onset, with all effect sizes below 0.1. Significant differences were found between control and self-selected phrases, with the control phrase showing higher CPPS (+2.6 dB), intensity (+2.7 dB SPL), and HNR (+4.3).

The crack-sob onset does not significantly alter objective measures of vocal fold adduction or vibratory stability during sustained high-intensity phonation in trained singers. The technique's reported benefits may be primarily perceptual rather than physiological, suggesting its value as a pedagogical tool for managing singer effort without compromising vocal function.