interval
D♯ major seventh
D♯lowerC𝄪upperM711 half steps
Eleven half steps: a half step short of the octave, which is why it leans on it.
On the keyboard
What is true of it
D♯ up a major seventh is C𝄪: 11 half steps, and 7 letters counting both ends.
Turn it upside down — put the D♯ on top — and it becomes a minor second. The two numbers always add to nine, and the two sizes to twelve.
It is a dissonance.
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♯ → Adiminished fifth · dissonanceD♯ → A♯perfect fifth · perfect consonanceD♯ → Bminor sixth · imperfect consonanceD♯ → B♯major sixth · imperfect consonanceD♯ → C♯minor seventh · dissonance