A7b9 guitar chord
The standard grips this chord is usually shown with.
- Tap a note to hear it
- Arrows change position
- Fingers, notes or intervals
- Play the chord
About A7b9 — 3rd inversion
A7b9 is A, C#, E, G and Bb — A9 with the ninth lowered a semitone.
It sounds dark and urgent. The flat ninth comes from the harmonic minor, so this is the V of a minor key rather than a major one.
Altered dominant — it points at a minor chord.
A7b9 notes and formula
| A | C# | E | G | Bb |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♭9 |
Also written A7(b9), A7-9 or A7♭9. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play A7b9
A7b9 in 3rd inversion puts G in the bass instead of A, the 7th of the chord. The notes are the same; what changes is what the bass line does, which is most of why you would reach for it — it lets the lowest voice move by step where the root would have jumped.
One of A7b9’s 6 common shapes does this:xx5656
Play A7b9 as a shell — root, third and seventh — and the spare string takes the #11 (D#), the b13 (F) or the 13 (F#).
All 6 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
- x02323, open position, A, root position, top note G, 1 open string
- 5453xx, 3rd fret, A, root position, top note Bb, all fretted
- xx5656, 5th fret, G, 3rd inversion, top note Bb, all fretted
- 575656, 5th fret, A, root position, top note Bb, barred
- xx7686, 6th fret, A, root position, top note Bb, all fretted
- x-12-11-12-11-12, 11th fret, A, root position, top note E, barred
How to use A7b9
A7b9 is a dominant with its tension raised, so it still points at D — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
In a phrase:Em7b5→A7b9→Dm7— the minor ii–V–i of D.
Voice by voice, A7b9 → Dm. 3 voices move by a semitone, and one note is common to both chords.
| In A7b9 | Moves | In Dm |
|---|---|---|
| A, the root | stays where it is | A, the fifth |
| C#, the major third | rises a semitone | D, the root |
| E, the fifth | rises a semitone | F, the minor third |
| G, the flat seventh | falls a whole tone | F, the minor third |
| Bb, the flat ninth | falls a semitone | A, the fifth |
What to play over A7b9
Every note of A7b9 is in A half-whole diminished.
Chords near A7b9
Change one note of A7b9 and you have A7 (drop the flat ninth), Aalt (the fifth becomes the sharp fifth), A9 (the flat ninth becomes the ninth), A7#9 (the flat ninth becomes the sharp ninth) or A/G (drop the flat ninth).
A7b9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.