Immediate Effects of Finger Kazoo Exercise With and Without Oropharyngeal Enlargement in the Operatic Singing Voice: A Randomized, Single-Blind, Crossover Controlled Clinical Trial

Objective This study examined the immediate effects of the Finger Kazoo (FK) exercise, with and without intentional oropharyngeal enlargement, on acoustic, self-perceptual, and auditory-perceptual parameters of the operatic singing voice. Methods Fifteen classically trained singers screened using the Singing Voice Handicap Index-10 performed two randomized conditions: FK without oropharyngeal enlargement (Condition A) and FK with oropharyngeal enlargement (Condition B). Assessments included: (1) self-perception using the Evaluation Auditory-Perceptual Instrument for Operatic Singing Voice—EAI Scale; (2) acoustic analysis of maximum phonation time (MPT) for vowels /a/ and /i/, examining fundamental frequency (F 0 ), jitter, and shimmer; and (3) blinded auditory-perceptual ratings of aria excerpts by a 15-member expert panel. Statistical procedures comprised paired and nonparametric tests ( t , Wilcoxon, and Friedman), robust analyses, and Bayes factors, with Holm-adjusted P values and effect sizes ( Cohen's d, r ). Results Both interventions significantly improved MPT and reduced jitter and shimmer (all p