What's the difference between guqin and heptachord?

Guqin

Definition:

Example Sentences:

Heptachord

Definition:

• (n.) A system of seven sounds.
• (n.) A lyre with seven chords.
• (n.) A composition sung to the sound of seven chords or tones.

Example Sentences:

• (1) The measured values obtained by both ordinary one-octave-interval and heptachord PMT are compared in this article.
• (2) We evaluated the reproducibility of measured values obtained using a heptachord pitch-matching test (PMT).