A7(b9) chord
The A dominant minor ninth chord (abbreviated "A7(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 dominant seventh chord.
In practice, the fifth (E) is often omitted from the A7(b9) chord because it's not always possible to play all notes simultaneously.
Name
A dominant minor ninth chord
Notes
A C♯ E G B♭
Intervals
1 3 5 ♭7 ♭9
Chord symbol
A7(b9)
Alternative symbol
A7b9
Type
Pentad (five-note chord)