hexachord

The three hexachords on G, C, and F respectively.

In music, not a chord in the true sense, but a group of six individual notes. Introduced in the 11th century as a method of sight-singing, a series of overlapping scalar hexachords embraced the entire compass of notes. In the 20th century the term was redefined by composers using the twelve-tone system, particularly Arnold Schoenberg and Anton Webern, as being half of a twelve-tone (twelve-note) row, allowing further compositional manipulation.