interval
D♯ diminished fifth
D♯lowerAupperd56 half steps
A perfect fifth narrowed by a half step. The interval inside every diminished triad.
On the keyboard
What is true of it
D♯ up a diminished fifth is A: 6 half steps, and 5 letters counting both ends.
Turn it upside down — put the D♯ 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: D♯ to G𝄪 is a fourth, D♯ to A is a fifth. They sound the same and behave differently.
Every interval on D♯
D♯ → Eminor second · dissonanceD♯ → E♯major second · dissonanceD♯ → F♯minor third · imperfect consonanceD♯ → F𝄪major third · imperfect consonanceD♯ → G♯perfect fourth · perfect consonanceD♯ → G𝄪augmented fourth · dissonanceD♯ → A♯perfect fifth · perfect consonanceD♯ → Bminor sixth · imperfect consonanceD♯ → B♯major sixth · imperfect consonanceD♯ → C♯minor seventh · dissonanceD♯ → C𝄪major seventh · dissonance