12:15:18:20

12:15:18:20, the just, classical, or ptolemaic major sixth chord, is a major sixth chord in the 5-limit, with steps 5/4, 6/5, and 10/9. It is an anomalous saturated suspension in the 9-odd-limit.

Chord information

Harmonics	12:15:18:20
Subharmonics	1/(15:12:10:9)
Intervals from root	1/1–5/4–3/2–5/3
Cents from root	0¢–386¢–702¢–884¢
Step intervals	5/4, 6/5, 10/9
Step cents	386¢, 316¢, 182¢
Color name	yo-6 or y6
Prime limit	5
Genus	32⋅5 (45)
Intervallic odd limit	9
Otonal odd limit	15
Utonal odd limit	15
Consistent edos (d ≥ 2)	12edo*, 19edo**, 34edo*, 38edo*, …
* 2 ≤ d < 4; ** 4 ≤ d < 8; *** 8 ≤ d < 16; …

See also

• Its homonym 10:12:15:18 (1/1–6/5–3/2–9/5), a minor seventh chord.