Music Theory Spectrum 42:2, 173–92

Toward the end of his 2012 book, Audacious Euphony, Richard Cohn asks, “how does music that is heard to be organized by diatonic tonality [as in the age of Mozart] become music that is heard to be organized in some other way [as in the age of Webern]”? In the present article, a theory different from Cohn’s is offered as answer. The theory’s three sub-theories, harmonic hierarchy, within-key chromaticism, and “solar” key distance, lead to a distinction between four types of harmonic systems: the strictly diatonic, the first- and second-order chromatic, and the restricted twelve-tone system. As its name implies, the latter harmonic system allows for twelve-tone levels, though under a restriction (termed Principle of Diatonic Fusion) that holds “the Webern in Mozart” in check.