Septimal chromatic semitone on C Playⓘ.Septimal chromatic semitone + octave Playⓘ.
In music, a septimal chromatic semitone or minor semitone[1] is the interval 21:20 (Playⓘ). It is about 84.47 cents. The septimal chromatic semitone may be derived from the harmonic series as the interval between the twentieth and twenty-first harmonics.