Heptachord
Heptachord , noun
[Greek "epta`chordos seven-stringed; "epta` seven + chordh` chord: compare French heptacorde. See Seven, and Chord.]
1.
(a) (Anc. Music) A system of seven sounds.
(b)
(Anc. Music) A lyre with seven chords.
2.
(Anc. Poet.) A composition sung to the sound of seven chords or tones. — Moore (Encyc. of Music)