Xenharmonic music

Xenharmonic music is music that uses a tuning system that is unlike the 12-tone equal temperament scale. It was named by Ivor Darreg, from the Greek xenos (Greek ξένος) meaning both foreign and hospitable. He stated that it was "intended to include just intonation and such temperaments as the 5-, 7-, and 11-tone, along with the higher-numbered really-microtonal systems as far as one wishes to go."

John Chalmers, author of Divisions of the Tetrachord, wrote, "The converse of this definition is that music which can be performed in 12-tone equal temperament without significant loss of its identity is not truly microtonal." Thus xenharmonic music may be distinguished from twelve-tone equal temperament, as well as use of intonation and equal temperaments, by the use of unfamiliar intervals, harmonies, and timbres.