Chord · A Dominant 7♭9
A7♭9 Chord
A7♭9 is A, C#, E, G and Bb — spicy V chord; minor-key resolution.
A7♭9 on every instrument
The same 5 notes, 2 sets of hands. Open a diagram for alternate shapes, audio and the mistakes to avoid.
What A7♭9 is made of
A7b9 (A seventh flat nine) is built from the notes A, C#, E, G, Bb, with the interval pattern 1, 3, 5, b7, b9.
Stack 1, 3, 5, b7 and b9 on a root of A and you get A, C#, E, G and Bb. That interval recipe is what makes the chord a seventh flat nine chord — move the same shape to another root and the character travels with it, which is why C7♭9 sounds like a transposed A7♭9.
Dominant 7♭9: Spicy V chord; minor-key resolution.
Spelling: the notes above are written the way a score would write them, not simplified to the nearest piano key. That is why this chord is spelled with C♯ rather than its enharmonic equivalent.
Keys that contain A7♭9
No major or natural-minor key contains all 5 of these notes — this one gets borrowed.
Chords like this one sit outside the diatonic set — they arrive as secondary dominants, borrowed chords or passing harmony. Browse every key to see which progressions pull it in.
Other chords on A
Same root, different colour.
The same seventh flat nine shape, moved
The identical interval recipe, built on other roots.
Questions people ask about A7b9
- What notes are in the A7b9 chord?
- A7b9 is made of A, C#, E, G and Bb — the 1, 3, 5, b7 and b9 degrees of a seventh flat nine chord built on A.
- What keys use the A7b9 chord?
- No major or natural-minor key contains all 5 notes of A7b9. Chords like this arrive as borrowed harmony — secondary dominants, harmonic-minor colour, or chromatic passing chords — rather than as one of a key's native chords.
- How do you play A7b9 on guitar and piano?
- This page shows A7b9 on guitar and piano — 6 voicings in total. Each diagram links to the full instrument page with alternate shapes, audio and common mistakes.
Learn the theory behind it
Why A7♭9 behaves the way it does — the guides that explain the chord instead of just spelling it.