Vibrato Synchronicity in Sustained Notes From Female Singers Blending to a Prerecorded Singer

Vibrato in the singing voice can be defined as a modulation in pitch, intensity, and timbre. It has been speculated and reported that vibrato affects blend in choral singing, with evidence that the interactions occurring during choral singing can lead to a coupling and entrainment of vibrato.

The aim of this study was to assess the vibrato modifications and vibrato interactions that can arise in blended group singing as compared to solo singing. We tested the hypothesis that when singers blend to another singer with vibrato, a degree of synchronization will occur in order to aid blend.

Individual female singers with vocal ranges from alto to soprano were recruited and asked to (1) sing with vibrato in a solo condition, and (2) blend with a prerecorded reference singer under different blending conditions. Isolated notes were held for approximately 5 to 7 seconds on the vowel /i/ and /a/ on pitches of an E major triad from E₄ to E₅. We calculated rate and extent; jitter and shimmer, to study the regularity associated to rate and extent; and recurrence quantification analysis (RQA), to detect phase synchronization.

Results show that singers modified their vibrato parameters of rate, extent, jitter, and shimmer in the blending condition. Additionally, participants were able to reach high levels of vibrato synchronization, which was negatively correlated with the vibrato regularity of rate during their baseline singing.

Whether synchronization of multiple vibratos is a conscious or unconscious strategy to blend is still unknown to singing research; however, we have presented further evidence of the presence of this phenomenon. This research is relevant for pedagogical practices across both solo singing and group singing and supports a need for future research to understand levels of entrainment that take place in group singing activities.