Analysis of intonation in unison choir singing

Abstract

Choir singers synchronize their fundamental frequency (f0) and timing when they perform together. In this work, we investigate several expressive characteristics of choir singing, with special emphasis on unison performances, to study how singers blend together and interact with each other by analyzing their f0 dispersion, intonation, and vibrato. We use the spectral autocorrelation algorithm to obtain the f0 trajectories of each individual singer and compute the f0 dispersion as the standard deviation of the f0 distribution. Using the Pearson correlation, we study the synchronization of singers in terms of their intonation and vibrato. Together with this study, we present a new choir singing dataset of voices singing together but recorded individually using directional close microphones. This dataset contains the individual recordings of 16 singers from a semiprofessional 4-part choir (SATB) performing 3 different songs. We found the f0 dispersion in unison sections to be in the range of 16 to 30 cents, and the largest average f0 dispersion was found in the basses. We observed that the intonation correlation varies a lot and is around 0.32 on average in all cases. The slowest piece was the one with the highest percentage of notes with vibrato, which had a frequency around 5 Hz for the whole dataset.