6:7:9
| Chord information |
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.
6:7:9 is the second-simplest otonal tertian triad, past 4:5:6, and is thus very consonant. The inverse of 6:7:9 is 14:18:21, the supermajor triad. These triads can be used in the same way as the 5-limit ones, leading to a septimal version of tertian harmony. However, this has a number of issues. First of all, 14:18:21 may sound unstable due to its relatively high otonal complexity. In addition, the 7/6 and 9/7 intervals differ by 54/49, an interval of 168 cents, unlike 5/4 and 6/5, which differ by 25/24, an interval only about 71 cents in size. This means the 6:7:9 and 14:18:21 chords don't contrast as well as the 5-limit 4:5:6 and 10:12:15 chords. Another important fact is that the 6:7:9 chord doesn't contain the root, though it is a subchord of 4:5:6:7:9 which does.
The 6:7:9 triad and its inverse 14:18:21 are nonetheless useful in tertian harmony, bringing new flavors not found in the 5-limit.
See also
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Todo: add sound example, research
This chord may be closely connected to 7-limit interpretations of the Blues scale. |