Hexachord

HEXACHORD. In order to remove certain grave difficulties connected with the Tetrachords of the Greek tonal system, Guido Aretinus is said to have proposed, about the year 1024, a new arrangement, based upon a more convenient division of the scale into Hexachords—groups of six sounds, so disposed as to place a diatonic semitone between the third and fourth notes of each series, the remaining intervals being represented by tones. The sounds of which these Hexachords are composed are sung, by the...