Tonality flux

Tonality flux is Harry Partch's term for the kinds of subtle harmonic changes that can occur in a microtonal context from notes moving from one chord to another by tiny increments of voice leading. For instance, within a major third G-B, there can be a minor third G to B, such that in moving from one to the other each line shifts less than a half-step. Within a just intonation scale, this could be represented (, indicates an approximate quarter-tone sharp, an approximate quarter-tone flat) by

One voice slides down from 386 cents to 347, the other slides up from 0 cents to 32, yet the harmonic shift can be dramatic. The best-known example of tonality flux, and one of the two Partch uses as illustration, is the beginning of his composition The Letter, in which the kithara alternates between two chords, one major and one minor, with the minor third of one nestled inside the major third of the other (given here in Ben Johnston's pitch notation):