interval
D♭ major seventh
D♭lowerCupperM711 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♭ → E♭♭minor second · dissonanceD♭ → E♭major second · dissonanceD♭ → F♭minor third · imperfect consonanceD♭ → Fmajor third · imperfect consonanceD♭ → G♭perfect fourth · perfect consonanceD♭ → Gaugmented fourth · dissonanceD♭ → A♭♭diminished fifth · dissonanceD♭ → A♭perfect fifth · perfect consonanceD♭ → B♭♭minor sixth · imperfect consonanceD♭ → B♭major sixth · imperfect consonanceD♭ → C♭minor seventh · dissonance