Equal or non-equal temperament in a capella SATB singing

Musical instruments whose pitch control is not fixed to specific notes, such as non-fretted stringed instruments and the human voice, have the freedom to vary the intonation of each note individually. A previous experiment to test whether an soprano, alto, tenor bass (SATB) a capella quartet made use of an equal or a non-equal tempered tuning system, indicated that the latter was the preference, and that singers tended to a form of just intonation for their tuning. That experiment made use of specially written SATB exercises consisting of a number of modulations between the starting and finishing chords, which themselves were either identical or exactly an octave apart. The intonation difference between the chords in the exercises was measured relative to just intonation and equal tempered tuning. Fundamental frequency data were gathered from each member of the quartet by means of four electrolaryngographs. This paper reports on the results of a second experiment with a different quartet which aims to establish the extent to which the effect might be replicated. The implications for conductors of a capella choirs are discussed.