Tone cluster
![Example of piano tone clusters. The clusters in the upper staff—C♯ D♯ F♯ G♯—are four successive black keys. The last two bars, played with overlapping hands, are a denser cluster.](/Images/godic/202502/16/Tone_cluster1638.JPG")
![The modern keyboard is designed for playing a diatonic scale on the white keys and a pentatonic scale on the black keys. Chromatic scales involve both. Three immediately adjacent keys produce a basic chromatic tone cluster.](/Images/godic/202502/16/Piano-keyboard1645.jpg")
![A thirteenth chord](/Images/godic/202502/16/Thirteenth_chord_collapsed1645.png")
![An example of Henry Cowell's notation of tone clusters for piano Play](/Images/godic/202502/16/Cowell_tone_clusters1645.png")
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.