28/27
| Interval information |
small septimal chroma,
subminor second,
septimal minor second,
trienstonic comma
reduced
[sound info]
The superparticular interval 28/27, septimal third-tone or small septimal chroma has the seventh triangular number as a numerator and is the difference between 15/14 and 10/9, 9/8 and 7/6, 9/7 and 4/3, 3/2 and 14/9, 12/7 and 16/9, and 9/5 and 28/15.
Although called a chroma for its proximity (and conflation in systems like septimal meantone) with the classic chroma 25/24, 28/27 is a diatonic semitone in both Helmholtz-Ellis notation and Functional Just System because it is 64/63 smaller than the Pythagorean minor second 256/243. Hence, it may be described as the septimal minor second or subminor second if treated as an interval in its own right. This is analogous to the septimal major second 8/7, which has the same relationship with 9/8, and such classification suggests the function of a strong leading tone added to the traditional harmony.
It is very accurately approximated by 19edo (1\19), and hence the enneadecal temperament.
On the other side of things, it may be called the trienstonic comma if treated as a comma to be tempered out, and in fact the trienstonic clan does exactly that.
See also
- 27/14 – its octave complement
- List of superparticular intervals
- Gallery of Just Intervals
- Trienstonic clan, where it is tempered out
- Wikipedia: Septimal third tone