Analysis of Interactive Intonation in Unaccompanied SATB Ensembles

Unaccompanied ensemble singing is common in many musical cultures, yet it requires great skill for singers to listen to each other and adjust their pitch to stay in tune. The aim of this research is to investigate interaction in four-part (SATB) singing from the point of view of pitch accuracy (intonation). In particular we compare intonation accuracy of individual singers and collaborative ensembles. 20 participants (five groups of four) sang two pieces of music in three different listening conditions: solo, with one vocal part missing and with all vocal parts. After semi-automatic pitch extraction and manual correction, we annotated the recordings and calculated the pitch error, melodic interval error, harmonic interval error and note stability. We observed significant differences between individual and interactional intonation, more specifically: 1) Singing without the bass part has less mean absolute pitch error than singing with all vocal parts; 2) Mean absolute melodic interval error increases when participants can hear the other parts; 3) Mean absolute harmonic interval error is higher in the one-way interaction condition than the two-way interaction condition; and 4) Singers produce more stable notes when singing solo than with their partners.