Analysis of Interactive Intonation in Unaccompanied SATB Ensembles

Singing with other singers is a common scene in practical performance and it is very hard to keep in tune. The aim of this research is to find an evidence of the interaction in SATB ensemble which makes a comparison of intonation accuracy of individual singers and collaborative ensembles. 20 participants distributed into 5 groups of \textit{a capella} ensemble to sing two pieces of music in three different listening condition: sing solo, sing with one vocal part missing and sing with all vocal parts. After semi-automatic pitch extraction and manual correcting, we annotated the recording and calculated the pitch error, melodic interval error, harmonic interval error and note stability. The results show a significant difference between individual and interactional intonation, more specifically:
1) Sing without bass part have less mean absolute pitch error than sing with all vocal parts.
2) Mean absolute melodic interval error does not influence by the listening condition.
3) One-way interaction condition has less mean absolute harmonic interval error than two-way interaction condition.
4) The singers have more stable notes when they sing solo then they sing with live partners.