6:7:9

6:7:9, the subminor triad or septimal minor triad, is a triad in the 7-limit sometimes used in place of a minor triad. It appears as a minor triad in the diatonic scale of superpyth, as 64/63 being tempered out means 32/27 is equated with 7/6. This is in contrast to meantone, where 32/27 is equated with 6/5, and thus the minor triad becomes 10:12:15.

Chord information

Harmonics	6:7:9
Subharmonics	1/(21:18:14)
Intervals from root	1/1–7/6–3/2
Cents from root	0¢–267¢–702¢
Step intervals	7/6, 9/7
Step cents	267¢, 435¢
Color name	zo or z
Prime limit	7
Genus	32⋅7 (63)
Intervallic odd limit	9
Otonal odd limit	9
Utonal odd limit	21
Consistent edos (d ≥ 2)	5edo*, 14edo*, 17edo*, 19edo*, …
* 2 ≤ d < 4; ** 4 ≤ d < 8; *** 8 ≤ d < 16; …

6:7:9 is the second-simplest otonal tertian triad, past 4:5:6, and is thus very consonant. However, its inverse, 14:18:21, may sound less stable due to its higher otonal complexity. In addition, the 7/6 and 9/7 intervals differ by 54/49, an interval of 168 cents, which means the subminor and supermajor triads don't contrast very well the same way 5-limit triads do. Nonetheless, these triads may be used in progressions together with the 5-limit ones.

See also

• 14:18:21 - the supermajor triad
• 6:7:9:10 - adds 5/3

Todo: expand, improve readability, research This chord may be closely connected to 7-limit interpretations of the Blues scale.