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