16/15

16/15 |4 -1 -1>

111.73129 cents

sound sample

The 5-limit just diatonic semitone is the superparticular interval 16/15 -- the difference between the major third 5/4 and the fourth 4/3, and between 3/2 and 8/5.

When this ratio is taken as a comma to be tempered, it produces father temperament, where 4/3 and 5/4 are equated. In this temperament, major thirds and fifths become octave-inverses of each other.