28/27

Interval information

Ratio	28/27
Factorization	22 × 3-3 × 7
Monzo	[2 -3 0 1⟩
Size in cents	62.9609¢
Names	small septimal chroma, septimal third-tone, subminor second, septimal minor second
Color name	z2, zo 2nd
FJS name	[math]\displaystyle{ \text{m2}^{7} }[/math]
Special properties	superparticular, reduced
Tenney height (log2 nd)	9.56224
Weil height (log2 max(n, d))	9.61471
Wilson height (sopfr(nd))	20
[sound info]
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The superparticular interval 28/27 (also small septimal chroma or septimal third-tone) 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.

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