Unlike fixed-pitch instruments, the voice requires careful regulation during each note in order to maintain a steady pitch. Previous studies have investigated aspects of singing performance such as intonation accuracy and pitch drift, treating pitch as fixed within notes, while the pitch trajectory within notes has hardly been investigated. The aim of this paper is to study pitch variation within vocal notes and ascertain what factors influence the various parts of a note. We recorded five SATB quartets singing two pieces of music in three different listening conditions, according to whether the singers can hear the other participants or not. After analysing all of the individual notes and extracting pitch over time, we observed the following regularities:
1) There are transient parts of approximately 120 ms duration at both the beginning and end of a note, where the pitch varies rapidly;
2) The shapes of transient parts differ significantly according to the adjacent pitch, although all singers tend to have a descending transient at the end of a note;
3) The trajectory shapes of female singers different from those of male singers at the beginnings of notes;
4) Between vocal parts, there is a tendency to expand harmonic intervals (by about 8 cents between adjacent voices).