Bitonisch

Bitonisch is a term in music theory used to describe the simultaneous use of two distinct tonal centers or keys within a single passage. In this texture, melodies or harmonies imply different keys, creating a sense of two tonics at once. The word derives from bi- meaning two and tonus meaning tone, and it is common in Dutch and German music literature; in English discussions the phenomenon is usually called bitonality or two-key harmony. Bitonisch is often viewed as a specific form of polytonality, generally referring to the concurrent presence of exactly two tonal centers rather than multiple keys.

In practice, bitonisch textures may arise from juxtaposing chords from different keys, or from independent voices anchored in different tonal centers. A primary key may be maintained alongside a secondary center that colors or contrasts with the main harmony, with the emphasis shifting over time. The effect ranges from clear separation of the two keys to more integrated textures where the two tonal centers inform melodic and harmonic decisions.

Historically, bitonisch textures emerged in the early 20th century as composers explored new harmonic possibilities. It is associated with modernist composers such as Bartók, Milhaud, and Stravinsky, among others, and can appear in works that mix tonal and serial techniques. In later periods, bitonality has continued to appear in experimental and contemporary music as a flexible tool for color, structure, and expressive contrast.

See also: polytonality, harmony, tonality.