Influences on pitch variation in a cappella choral singing

One of the most important aspects of choral singing is the ability to sing in tune with the other members of the choir. Singing in tune within a choir does require each singer engaging in careful and focussed listening to the other parts to establish the placement of the pitches of their individual notes within their own part. Simply singing in tune with, for example, notes played on a piano will not result the most 'settled', 'beautiful' or 'consonant' tuning due to the use of equal tempered tuning - twelve equal semitones in each octave on a piano. It is the use of 'just intonation' during a cappella or unaccompanied singing that has the potential to result in more settled, beautiful or consonant tuning, which results from focussed and careful listening to pitch. However, there are other complicating factors when striving to sing in tune. It turns out that the human hearing system additionally uses other aspects of acoustic signals when it is engaged in pitch perception, most notably, timbre (note 'quality') perception. These matters are described along with their implications for overall individual and choral tuning.