Tone cluster

A tone cluster is a musical chord comprising consecutive tones in a scale. Prototypical tone clusters are based on the chromatic scale, and are separated by semitones. For instance, three adjacent piano keys (like C, C#, and D) struck simultaneously produce a tone cluster. Variants of the tone cluster include chords comprising consecutive tones separated diatonically, pentatonically, or microtonally. On the piano, such clusters often involve the simultaneous striking of successive white or black keys.

In the 1910s, composer-pianists Leo Ornstein and Henry Cowell made the first extensive use of tone clusters in Western classical music. During the same period, Charles Ives employed them in several compositions that were not publicly performed until the late 1920s or 1930s. Béla Bartók and, later, John Cage and Giacinto Scelsi became proponents of the tone cluster. Today, tone clusters play a significant role in free jazz.

In most Western music, tone clusters tend to be heard as dissonant. Keyboard instruments, because of the arrangement of the playing area, particularly lend themselves to the performance of tone clusters, but clusters may be performed with almost any individual instrument on which three or more notes can be played simultaneously, as well as by most groups of instruments.