Trichord

In music theory, a trichord is a group of three different pitch classes found within a larger group (Friedmann 1990, 42). For example a contiguous three-note set from a musical scale (Houlahan & Tacka 2008, 54) or a twelve-tone row. The term is derived by analogy from the 20th-century use of the word "tetrachord". Unlike the tetrachord and hexachord, there is no traditional standard scale arrangement of three notes, nor is the trichord necessarily thought of as a harmonic entity (Rushton 2001).