A9 Chord
A9 is a dominant seventh plus B, the ninth. Its full spelling has five different notes, so a practical guitar or ukulele grip may leave out a less essential chord tone.
- Notes: A-C sharp-E-G-B
- Symbol: A9
- V9 in D major
- Seventh and ninth
A9
How to play an A9 chord
Notes: A - C# - E - G - BA9
Root position
A - C# - E - G - B1st inversion
C# - E - G - B - A2nd inversion
E - G - B - A - C#3rd inversion
G - B - A - C# - E
Where does A9 belong?
In D major, A9 extends the V7 chord before it resolves to the tonic.
Play the role cards to hear how its surrounding chords change the job it does; Diatonic Chords explains the basic numbered roles.
- Dominant with a ninthV9
A V7 with the ninth on top: the same pull to D, a fuller sound.
DGA9V9D - Funk and blues homeI9
In funk and blues this is a home chord that never has to resolve.
A9I9D9A9E9
Progressions to try
- DGA9D
A9 is V9 in D major; its seventh keeps the dominant pull while the ninth adds another voice.
- A9D9A9E9
Treat the repeated A9 as a blues home chord, then hear the other ninth chords answer it.
Which shape should you use?
On guitar, the open shape x02423 is the easiest place to start. The barre shape 575657, at the 5th fret, moves the chord up the neck and sits well between other barre chords.
On ukulele, the open shape 4130 is the easiest place to start. 4754 gives a higher version.
On piano, spread the five-note spelling across both hands: A-C sharp-E-G-B. Move A up an octave to reach the first inversion, C sharp-E-G-B-A; the notes remain the same while the lowest voice changes.
What are the inversions?
The first four notes, A-C sharp-E-G, form the dominant seventh. B adds the ninth.
- Root position: A-C sharp-E-G-B, with A lowest.
- First inversion: C sharp-E-G-B-A, written A9/C# if C sharp is lowest in the whole arrangement.
- Second inversion: E-G-B-A-C sharp, written A9/E if E is lowest in the whole arrangement.
- Third inversion: G-B-A-C sharp-E, written A9/G if G is lowest in the whole arrangement.
- Fourth inversion: B-A-C sharp-E-G, written A9/B if B is lowest in the whole arrangement.
A slash chord names the note in the bass, not merely the lowest note under one hand. Chord Inversions shows how to read that distinction.
How does A9 differ from A7?
Remove the ninth, B, and the remaining notes form A7. The seventh stays, so both chords can still pull toward the same tonic. Try that one-note change on piano, then use the comparer to hear it in the full chord. See A7 for the other chord's full spelling and roles.
A9
A - C# - E - G - BA7
A - C# - E - G