A7b9 A dominant seventh flat nine chord
- Notes
- A C# E G Bb
- Formula
- 1 3 5 b7 b9
- Semitones
- 0 4 7 10 13 above the root
- Other symbols
- A7(b9), A7-9
A to C# is a major third (4 semitones), C# to E is a minor third (3 semitones), E to G is a minor third (3 semitones), G to Bb is a minor third (3 semitones). A dominant seventh with a flattened ninth, Bb, a half step (plus an octave) above the root. It is the sharpest-sounding of the common dominant chords and pulls hard towards a minor tonic.
A7b9 on the piano
Root position from A4: A4, C#5, E5, G5, Bb5. Middle C is C4.
A7b9 on the guitar
Standard tuning (E A D G B E). Strings run low E on the left to high e on the right, frets downwards; × is a muted string, ○ an open string, and each dot shows the note it sounds, with the root in blue-green. Every shape below has A as its lowest note.
5 x 5 6 5 6 (low E to high e)
Sounds A2 G3 C#4 E4 Bb4
x 12 11 12 11 x (low E to high e)
Sounds A3 C#4 G4 Bb4, fifth left out
The E-shape and A-shape grips are movable: an E-shape chord's root is the note under your first finger on the low E string, an A-shape chord's root is the note on the A string. Slide the same grip up or down to play dominant seventh flat nine chords on other roots.
Inversions of A7b9
An inversion puts a note other than the root in the bass. The name is what semicord's chord finder calls those notes played bottom to top; a slash name like C/E means a C chord with E in the bass.
| Position | Notes, bass first | Named | Listen |
|---|---|---|---|
| Root position | A C# E G Bb | A7b9 | |
| 1st inversion | C# E G Bb A | A7b9/C# | |
| 2nd inversion | E G Bb A C# | A7b9/E | |
| 3rd inversion | G Bb A C# E | A7b9/G | |
| 4th inversion | Bb A C# E G | A7/Bb (also read as A7b9/Bb) |
Where A7b9 fits
A7b9 is V7b9 in D minor. Its upper four notes C# E G Bb are C#dim7, so A7b9 and that diminished seventh are interchangeable over a A bass. The flat ninth Bb falls a half step to the fifth of Dm.