hexachord: Meaning and Definition of

hex•a•chord

Pronunciation: (hek'su-kôrd"), [key]
— n. Music.
  1. a diatonic series of six tones having, in medieval music, a half step between the third and fourth tones and whole steps between the others.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.