Influence of vowels on note pitching in a cappella vocal quartet performance

This paper notes that accurate tuning in a cappella (unaccompanied) choral music is a two-step process requiring (1) making pitch shifts on individual notes to sing intervals in just intonation thereby providing beat-free tuning for the consonant musical intervals that underpin the underlying harmony and (2) tuning different vowels to account for any additional pitch changes that are made in the context of the intrinsic pitch relating to the specific vowel being produced. This paper explores the second of these in the context of a part-by-part vowel variation during a sustained chord sung by the other three parts by a quartet of professional singers.This study aimed to investigate the relationship between the fundamental frequencies employed when singing different vowels on the same pitch for each member in turn of a professional soprano, alto, tenor, bass (SATB) a cappella vocal quartet in terms of the measured fundamental frequency during the production of a set of individual vowels within a four-part carrier phrase.This is an experimental singing production study on the tuning of vowels in the context of a cappella quartet singing. To facilitate this, one singer at a time in a professional a cappella vocal quartet changed the vowel they are singing on a single note concurrent with a consonant a cappella triad being sustained by the other three singers singing a fixed vowel.The first few bars of the a cappella anthem "If ye love me" by Thomas Tallis provided a carrier phrase that ended with a held chord on the chord on the word "me" by three singers against which the remaining singer produced a set of different vowels on their note of the chord. This is carried out for each of the four singers. The hypothesis being investigated is to remain accurately in-tune; fundamental frequency should be varied depending on the vowel being sung. Fundamental frequencies were measured using electrolaryngographs to ensure that there was no acoustic interference that could affect the accuracy of the fundamental frequency measurements if they were obtained from the audio output.The results provide clear evidence of changes being made to the fundamental frequencies of different vowels in an a cappella quartet context, and these changes confirm variations found elsewhere relating to the perceived pitches of different vowels.Measurable and consistent fundamental frequency variations occur when one part tunes different vowels against a reference chord sung by the other three singers in a choral quartet context on a fixed vowel. This has a direct consequence for tuning in a cappella choral music. The importance of carefully tuning individual notes for different vowels in a cappella choral singing requires focused listening to the pitches of the sounds being produced by the other singers in the choir. Usually, all parts are singing common vowels where it is important that the vowels are matched by being carefully blended together and tuning is aimed at being beat-free in just intonation. When compositions require parts to sing different vowels, both intrinsic (production related) and auditory (hearing related) pitch variations become relevant and challenge beat-free tuning.