polytonale

Polytonality, or polytonal music, refers to the simultaneous use of two or more distinct tonal centers or keys within a composition. In Italian, the adjective is polytonale.

The approach emerged in the early 20th century as composers sought to expand harmonic language beyond traditional major and minor tonality. It is distinct from atonality and from simple bitonality; polytonality can place different keys on different musical strands, sometimes with independent rhythms or melodies. Techniques include polychords, where chords from different keys are stacked, and the layering of keys across instrumental or vocal lines.

Notable practitioners include Charles Ives, who layered keys in American hymns and marches; Darius Milhaud, whose polytonal style is evident in works like Le boeuf sur le toit and La création du monde; and Igor Stravinsky, who experimented with polytonality in the early and mid-20th century.

Impact and legacy: polytonality broadened the harmonic vocabulary of modern music and influenced later post-tonal languages. It remains a recognized technique in concert music and has also appeared in film scores and other contemporary contexts.