The interval whose frequency ratio is 7/6 (267 cents [¢]).
Another subminor-3rd is the 5-limit ratio 75:64 (= ~274.6 cents), used by Joe Monzo in his piece 3 Plus 4 specifically for the slightly different sound it has from 7:6.
The subminor-3rd is a categorical musical interval within about +/- 10 cents of 267 cents.
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