A#7(b9) chord
The A-sharp dominant minor ninth chord (abbreviated "A#7(b9) chord") is a five-note chord consisting of the notes A♯, C, E♯, G♯, and B. The chord is formed by adding a major ninth to a A-sharp dominant seventh chord.
In practice, the fifth (E♯) is often omitted from the A#7(b9) chord because it's not always possible to play all notes simultaneously.
Name
A-sharp dominant minor ninth chord
Notes
A♯ C E♯ G♯ B
Intervals
1 3 5 ♭7 ♭9
Chord symbol
A♯7(b9)
Alternative symbol
A♯7b9
Type
pentad (five-note chord)