81/70

Interval information

Ratio	81/70
Factorization	2-1 × 34 × 5-1 × 7-1
Monzo	[-1 4 -1 -1⟩
Size in cents	252.6804¢
Name	septimal ultramajor second
Color name	rg2, rugu 2nd
FJS name	[math]\displaystyle{ \text{M2}_{35} }[/math]
Special properties	reduced
Tenney norm (log2 nd)	12.4691
Weil norm (log2 max(n, d))	12.6797
Wilson norm (sopfr(nd))	26
[sound info]
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81/70, the septimal ultramajor second is a 7-limit interseptimal ratio of about 253 cents. It is sharp of a major second 9/8 by a septimal quartertone 36/35, sharp of a supermajor second 8/7 by a syntonic comma 81/80, and flat of a subminor third 7/6 by a sensamagic comma 245/243.

Notice it is also flat of the just minor third 6/5 by a subminor second 28/27. For this fact it is useful in the sensamagic dominant chord where it functions as a dissonance yet to be resolved up to the minor third. The canou temperament targets this progression and uses it as one of the generators.

Approximation

It is perfectly approximated by 19edo (4\19), with an error of 0.05 cents, and hence equally well done by the enneadecal temperament.

See also

• 140/81 – its octave complement
• 35/27 – its fifth complement
• Gallery of just intervals