21/20

Interval information

Ratio	21/20
Factorization	2-2 × 3 × 5-1 × 7
Monzo	[-2 1 -1 1⟩
Size in cents	84.46719¢
Names	minor semitone, large septimal chromatic semitone
Color name	zg2, zogu 2nd
FJS name	[math]\displaystyle{ \text{m2}^{7}_{5} }[/math]
Special properties	superparticular, reduced
Tenney height (log2 nd)	8.71425
Weil height (log2 max(n, d))	8.78463
Wilson height (sopfr(nd))	19
[sound info]
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A small semitone, 21/20 may be found in 7-limit just intonation as, for example, the difference between 8/7 and 6/5, or between 5/3 and 7/4.

http://en.wikipedia.org/wiki/Septimal_chromatic_semitone