Fig. 1 · Bb to Ab

interval

B♭ minor seventh

B♭lowerA♭upperm710 half steps

Ten half steps. The interval that sits on top of a dominant seventh chord.

On the keyboard

BbAb
Fig. 2

What is true of it

B♭ up a minor seventh is A♭: 10 half steps, and 7 letters counting both ends.

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

It is a dissonance.

Every interval on B♭

B♭ → C♭minor second · dissonanceB♭ → Cmajor second · dissonanceB♭ → D♭minor third · imperfect consonanceB♭ → Dmajor third · imperfect consonanceB♭ → E♭perfect fourth · perfect consonanceB♭ → Eaugmented fourth · dissonanceB♭ → F♭diminished fifth · dissonanceB♭ → Fperfect fifth · perfect consonanceB♭ → G♭minor sixth · imperfect consonanceB♭ → Gmajor sixth · imperfect consonanceB♭ → Amajor seventh · dissonance

C m7C♯ m7D♭ m7D m7D♯ m7E♭ m7E m7F m7all 204