A9 chord on piano
A9 (A dominant 9th) is a dominant 9th chord built on A. It has 5 notes, A, C♯, E, G and B, and its formula is 1 3 5 ♭7 9.
Notes and intervals of A9
From the root upwards, A9 contains root (A), major 3rd (C♯), perfect 5th (E), minor 7th (G) and major 9th (B). Those intervals give the chord its colour: the formula 1 3 5 ♭7 9 works the same way in every key, so once you know it for A you can build the chord on any note.
| Degree | Interval | Note |
|---|---|---|
| 1 | root | A |
| 3 | major 3rd | C♯ |
| 5 | perfect 5th | E |
| ♭7 | minor 7th | G |
| 9 | major 9th | B |
How to play A9 on piano
Find A and play A, C♯, E, G and B together. With the right hand, a common fingering is 1-2-3-4-5. With the left hand, reverse it (5-4-3-2-1). Keep your wrist level and let the fingers curve, so all 5 keys go down at the same time.
Inversions of A9
An inversion keeps the same notes but puts another one in the bass. A9 has 3 inversions besides root position: 1st inversion (C♯ E G B A), 2nd inversion (E G B A C♯) and 3rd inversion (G B A C♯ E). Inversions let you move between chords with tiny hand movements, which is how pianists make progressions sound smooth.
Which keys use A9?
A9 is not built from the notes of a single major key, so it usually appears as a colour chord: a borrowed chord, a passing chord or a suspension that resolves to the next chord.
Scales to play over A9
To improvise over A9, start with A Mixolydian mode. All of these scales contain every note of the chord: A Mixolydian mode. Aim for the chord notes on strong beats and use the other notes to move between them.
About dominant 9th chords
A dominant seventh with a 9th on top: 1 3 5 ♭7 9. It keeps the tension of the 7 chord but sounds fuller, smoother and funkier, as the major ninth softens the tritone between 3 and ♭7. It belongs to the extended chords, built by stacking thirds beyond the seventh. For example C9: C E G B♭ D.
Use it wherever a V7 works: V9 to I, the dominant in ii7 V9 Imaj7, and every chord of a blues (I9 IV9 V9). Funk can sit on one 9 chord for a whole groove, and soul, gospel and jazz use it as a richer dominant. In minor keys, V7♭9 is more common than V9, because the scale has a ♭6.
Five notes are a lot: drop the fifth first, and the root too when a bass player has it. A classic split: root and ♭7 in the left hand, 3, 5 and 9 in the right. Rootless voicings such as 3 5 ♭7 9 or ♭7 9 3 5 are the standard jazz piano sound for dominant chords.
9 is not add9: a 9 chord has the ♭7, an add9 does not. 9 is not maj9 either: maj9 has the major seventh and a calm, non-dominant sound. And the 9 is a major ninth; ♭9 and ♯9 (as in E7♯9, the 'Hendrix chord') are altered versions with their own symbols.
Frequently asked questions
What notes are in the A9 chord?
A9 (A dominant 9th) contains A, C♯, E, G and B. In intervals: root (A), major 3rd (C♯), perfect 5th (E), minor 7th (G) and major 9th (B).
How do you play A9 on piano?
Play A, C♯, E, G and B together with the right-hand fingering 1-2-3-4-5. You can also play it in 3 inversions, shown on this page.
What scale goes with A9?
A Mixolydian mode fits A9 best. Other scales that contain all its notes: A Mixolydian mode.
What key is A9 in?
A9 does not belong to a single major key. It is used as a colour chord that borrows notes from outside the key.
Related
Ready to go further than the chart?
The free GuitarHarmony workshop shows every scale on the whole neck, names any chord you play and builds progressions with you. Free account, no card.