Fig. 1 · F# to D

interval

F♯ minor sixth

F♯lowerDupperm68 half steps

Eight half steps. The major third turned upside down.

On the keyboard

DF#
Fig. 2

What is true of it

F♯ up a minor sixth is D: 8 half steps, and 6 letters counting both ends.

Turn it upside down — put the F♯ on top — and it becomes a major third. The two numbers always add to nine, and the two sizes to twelve.

It is a imperfect consonance.

Every interval on F♯

F♯ → Gminor second · dissonanceF♯ → G♯major second · dissonanceF♯ → Aminor third · imperfect consonanceF♯ → A♯major third · imperfect consonanceF♯ → Bperfect fourth · perfect consonanceF♯ → B♯augmented fourth · dissonanceF♯ → Cdiminished fifth · dissonanceF♯ → C♯perfect fifth · perfect consonanceF♯ → D♯major sixth · imperfect consonanceF♯ → Eminor seventh · dissonanceF♯ → E♯major seventh · dissonance

C m6C♯ m6D♭ m6D m6D♯ m6E♭ m6E m6F m6all 204