List of pieces using polytonality and/or bitonality. This term is also used as a response to Van den Toorn's analysis against polytonality. Williams combined polytonality and the Lydian mode to express a mystic, dreamlike, and heroic quality. In addition, he showed an interest in twentieth-century techniques such as polyrhythms and polytonality. During these years Crawford began to incorporate polytonality and tone clusters into her compositions . The harmony is traditional; no influences of atonality or polytonality can be found. His compositions are influenced by jazz and Brazilian music and make extensive use of polytonality. His technique included the use of polytonality, polyrhythm, tone clusters, aleatoric elements, and quarter tones. Lithuanian traditional singing style sutartines is based on polytonality. The use of polychords may suggest bitonality or polytonality. Polytonality in harmony is another side of his stylistic language. Atonality and polytonality are among the techniques used in his later works. His "Concerto del dispetto" of 1959 integrates serialism and polytonality. Polytonality requires the presentation of simultaneous key-centers. Whole-tone scales and polytonality are foreign to music of the Classical era.