81/70

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Interval information
Ratio 81/70
Monzo [-1 4 -1 -1
Size in cents 252.6804
Name(s) septimal ultramajor second
Color name rg2, rugu 2nd
FJS name M235

[sound info]
open this interval in xen-calc

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

See also