Intonation and Staying in Tune in A Cappella Choral Singing

The tendency for singers to use non-equal temperament when singing unaccompanied or a cappella can have a large effect on the overall pitch stability of a piece of music, especially if there are several modulations. This chapter describes the background to this effect in terms of the temperament that is naturally adopted in a cappella singing and demonstrates how it can be predicted in practice. Results are presented from experimental measurements of the pitches used by a four-part SATB (soprano, alto, tenor, bass) quartet when they sing specially composed exercises and items from the a cappella choral repertoire, and these demonstrate the effect in practice. These experiments make use of four electrolaryngographs to measure the fundamental frequencies from each singer with an absence of cross interference. Pitch shifts that follow the trends suggested by the predictions are demonstrated for both the exercises and items from the a cappella choral repertoire.