Modelling Intonation and Interaction in Vocal Ensembles

Abstract

Voice is our native instrument and singing is the most universal form of music-making. As an important feature of singing, intonation accuracy has been investigated in previous studies, but the effect of interaction between singers has not been explored in detail. The aim of this research is to investigate interaction between singers in vocal ensembles, with a particular emphasis on how singers negotiate a joint reference pitch as the music unfolds over time. This thesis reports the results of three experiments which contribute to the scientific understanding of intonation. The first experiment tested how singers respond to controlled stimuli containing time-varying pitches. It was found that time-varying stimuli are more difficult to imitate than constant pitches, as measured by absolute pitch error. The results indicate that pitch difference, transient duration, and stimulus type have a significant influence on pitch error, and the instability of the acoustic reference has a positive correlation with pitch error. The second experiment measured pitch accuracy and interaction in unaccompanied unison and duet singing. The results confirm that interaction exists between vocal parts and influences the intonation accuracy. The results show that vocal part, singing condition (unison or duet), and listening condition (with or without a partner) have a significant effect on pitch accuracy, which leads to a linear mixed effect model describing the interaction by effect size and influencing factors. In the third experiment, the effect of interaction on both intonation accuracy and the pitch trajectory was tested in four-part singing ensembles. The results show: singing without the bass part has less mean absolute pitch error than singing with all vocal parts; mean absolute melodic interval error increases when participants can hear the other parts; mean absolute harmonic interval error is higher in the one-way interaction condition than the two-way interaction condition; and the shape of note trajectories varies according to adjacent pitch, musical training and sex.