The combination of two keys simultaneously. Just one example is Charles Ives’s Psalm 67, which was originally written and performed in 1898. Here two choral groups sing opposed triads – C major and G minor. The harmonic clashes of bitonality may be mysterious (as in the Ives piece), plangent, or acerbic. Bitonality is particularly associated with the music of Darius Milhaud (1892-1974).