Participants: Theodora Nestorova, John Mac Master, Isabelle Cossette and Gary Scavone

Period: 2021 - 2025

This dissertation presents a cross-disciplinary compendium of acoustic, perceptual, and biomechanic studies on naturally-occurring, time-varying vocal vibrato across several musical genres. Vibrato is a complex, multi-factorial feature tied to singing technique and artistry that is both volitionally and non-volitionally controlled by the vocalist.

A comprehensive literature review of existing research identifies the need for advanced analytical tools accounting for vibrato's complexity and time-variant nature. Existing vibrato analysis methods are based on calculating averages that do not consider ecologically valid time domain-based changes in singing. Normative vibrato standards are derived from Western Classical singing studies, signaling a lack of diversity. This culturally biased gap overlooks other music styles and aesthetic traditions, leading to misrepresentation and mischaracterization of vibrato.

To address these challenges, a methodological study introduces a novel theoretical framework to classify vibrato patterns into half-extent time profile archetypes. Focusing on professional singing samples drawn from Opera, Musical Theatre, and Jazz genres, the study proposes novel parametric techniques for vibrato analysis, providing a systematic approach including Coefficient of Variation, 4-PL regression models, and new metrics like Vibrato Onset Time to differentiate vibrato types.

A cross-sectional perceptual study examines how vibrato variability influences timbre semantics, analyzing cognitive interpretations from vocalists and instrumentalists describing unaccompanied vocal stimuli sung by professional singers. Using qualitative content vocabulary and thematic analysis, the study reveals frequent mentions of vibrato and strong correlations between vibrato variability and perceived vocal function. Findings underscore the perceptual validity and salience of temporally variant vibrato and its relevance for future assessment methodologies.

Field recordings collected in the Balkan Mountains enable acoustic analysis of vibrato in Bulgarian Folk Singing. Results highlight distinctive vibrato patterns and their function within traditional performance practices, expanding the scope of vibrato research to an Eastern musical tradition known for its distinctive vocal styles. Highly complex, multiphasic vibrato contours and unique vibrato patterns are interpreted alongside effective teaching strategies of cultural-pedagogical significance.

As no consensus or codified pedagogy exists on addressing vibrato in teaching contexts, an integrative investigation synthesizes the practical application of scientific vibrato research. Direct (explicit) vs. indirect (implicit) instruction using variable vibrato as a more comprehensive and style-specific diagnostic tool for assessment and training is explored. Created exercises promoting vibrato versatility and efficiency are recommended.

Building on these foundations, vibrato variability, its potential as a diagnostic tool, and its parallel to tremor are investigated. A pilot study leverages machine learning to assess vibrato as a biomarker for functional and neurogenic voice disorders, with applications in clinical and pedagogical contexts. The study further explores vibrato as an indicator of vocal stress and proposes methods for integrating vibrato analysis into vocal health assessments.

By integrating perceptual research, computational modeling, ethnographic analysis, and pedagogical innovation, this dissertation advances the field of vibrato studies. These interdisciplinary, mixed methods studies demonstrate vibrato variability as perceptually salient and propose a more genre-inclusive system of complex, time-varying vibrato acoustic parameters beyond averages. The implications of this research to evidence-based pedagogical and medical/clinical practices have the potential to transform and modernize vibrato training in singing teaching and vocal health rehabilitation in voice therapy.

• Nestorova, T. (2026) “To teach or not to teach vibrato?: Implicit versus explicit instruction in the vocal studio; Part I: Vibrato pedagogy in past to present pedagogical trends.”, “Part II: Practical and applicable tools, tips, and tricks.” Journal of Singing, Manuscript accepted for publication.
• Nestorova, T., Reymore, L., Marchand Knight, J., Soden, K., Smith, B., & McAdams, S. (2025) “Speaking of vocal vibrato: Timbre perceptions and semantic descriptions with pedagogical and rehabilitative implications.” Voice and Speech Review, Advance online publication.
• Nestorova, T., Aleksandrov, I., Gilbert, J. B., & Howell, I. (2024) “Does vibrato define genre or vice versa?: A novel approach to vocal vibrato analysis.” Journal of Voice, Advance online publication. https://doi.org/10.1021/j.jvoice.2024.12.01
• Nestorova, T., Brandner, M., Gingras, B., & Herbst, C. T. (2022). “Vocal vibrato characteristics in historical and contemporary opera, operetta, and Schlager.” Journal of Voice, Advance online publication. https://doi.org/10.1016/j.jvoice.2022.12.027