'Heptachord' definitions:

Definition of 'Heptachord'

From: GCIDE

Heptachord \Hep"ta*chord\, n. [Gr. "epta`chordos seven-stringed; "epta` seven + chordh` chord: cf. F. heptacorde. See Seven, and Chord.]
1. (Anc. Mus.) (a) A system of seven sounds. (b) A lyre with seven chords. [1913 Webster]
2. (Anc. Poet.) A composition sung to the sound of seven chords or tones. --Moore (Encyc. of Music). [1913 Webster]