Fig. 1 · A# to B

interval

A♯ minor second

A♯lowerBupperm21 half steps

One half step, written as a second: the smallest distance between two notes with different letters.

On the keyboard

BA#
Fig. 2

What is true of it

A♯ up a minor second is B: 1 half step, and 2 letters counting both ends.

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

It is a dissonance.

Every interval on A♯

A♯ → B♯major second · dissonanceA♯ → C♯minor third · imperfect consonanceA♯ → C𝄪major third · imperfect consonanceA♯ → D♯perfect fourth · perfect consonanceA♯ → D𝄪augmented fourth · dissonanceA♯ → Ediminished fifth · dissonanceA♯ → E♯perfect fifth · perfect consonanceA♯ → F♯minor sixth · imperfect consonanceA♯ → F𝄪major sixth · imperfect consonanceA♯ → G♯minor seventh · dissonanceA♯ → G𝄪major seventh · dissonance

C m2C♯ m2D♭ m2D m2D♯ m2E♭ m2E m2F m2all 204