heptachord

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 ]