A model of the perceptual root(S) of a chord accounting for voicing and prevailing tonality

Abstract

A theory of harmony is presented that predicts the perceptual root of any simultaneity within the chromatic scale, embedded in the context of any chord progression. The theory takes into account the pitch classes (pcs) of the chord, its voicing, the prevailing tonality, and local voice-leading. Pcs: the perceptual root of an isolated, octave-generalized chord is determined by the root-support intervals P1, P5, M3, m7 and M2. Voicing: other things being equal, the bass note is more likely to function as the root than the other notes. Tonality: the harmonic profile of a chord in a tonal context is given by the sum of the chord's profile in isolation and the pc-stability profile of the prevailing tonality. Voice leading: parallel movement of parts increases the likelihood that the roots of two sonorities will be heard to move in parallel with the voices. Predictions of the theory for the perceptual roots of diatonic triads and 7ths and of common chromatic chords in major and minor keys are intuitively reasonable, but will need to be tested against the results of perceptual-cognitive experiments and systematic studies of scores and improvised performances.