Fig. 1 · Gb to Dbb

interval

G♭ diminished fifth

G♭lowerD♭♭upperd56 half steps

A perfect fifth narrowed by a half step. The interval inside every diminished triad.

On the keyboard

Fig. 2

What is true of it

G♭ up a diminished fifth is D♭♭: 6 half steps, and 5 letters counting both ends.

Turn it upside down — put the G♭ on top — and it becomes a augmented fourth. The two numbers always add to nine, and the two sizes to twelve.

It is a dissonance.

Six half steps can be written two ways: G♭ to C is a fourth, G♭ to D♭♭ is a fifth. They sound the same and behave differently.

Every interval on G♭

G♭ → A♭♭minor second · dissonance G♭ → A♭major second · dissonance G♭ → B♭♭minor third · imperfect consonance G♭ → B♭major third · imperfect consonance G♭ → C♭perfect fourth · perfect consonance G♭ → Caugmented fourth · dissonance G♭ → D♭perfect fifth · perfect consonance G♭ → E♭♭minor sixth · imperfect consonance G♭ → E♭major sixth · imperfect consonance G♭ → F♭minor seventh · dissonance G♭ → Fmajor seventh · dissonance

C d5 C♯ d5 D♭ d5 D d5 D♯ d5 E♭ d5 E d5 F d5 all 204