polytonality

Polytonality layers two or more keys on top of each other — for instance, a melody in C major over an accompaniment in F-sharp major. The technique creates a distinctive "wrong-note" quality that is neither fully consonant nor fully atonal. Charles Ives was an early pioneer, layering hymn tunes and marches in different keys to recreate the experience of hearing multiple bands playing simultaneously in a New England town square. Darius Milhaud systematized polytonal techniques in works like his ballet La Création du monde, which stacks up to four or five keys simultaneously. Stravinsky's Petrushka chord (C major over F-sharp major) became one of the most famous polytonal sonorities. Bartók, Prokofiev, and Copland all employed polytonality. The technique differs from atonality — in polytonal music, individual lines are clearly tonal; it is only their combination that creates dissonance. This quality gives polytonal music a playful, sometimes satirical edge that pure atonality lacks.