heptadecad Mus.
(hɛptəˈdɛkəd)
[f. hepta- + decad.]
A scheme of twenty-four tones formed by the combination of seven decads, in the duodenal system of analysis.
| 1874 A. J. Ellis in Proc. R. Soc. XXIII. 14 The Harmonic Heptadecad or Unit of Modulation (or Decadation) consists of seven interwoven decads, which are constructed on the seven tones of a heptad as tonics, and contains 24 tones. |