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A 9th chord on guitar (A9)
Also called or written A9 or A
A 9th is built from A, C♯, E, G and B. This advanced barre shape at the 4th fret needs a strong index barre and a clean high-e mute.
How it is built
Formula 1, 3, 5, ♭7, 9
- Root positionA–C♯–E–G–BA95-4-5-4-5-×
- First inversionC♯–E–G–B–AA9/C♯×-4-5-4-5-5
- Second inversionE–G–B–A–C♯A9/E0-2-×-2-2-3
- Third inversionG–B–A–C♯–EA9/G3-2-2-2-2-3
- Fourth inversionB–A–C♯–E–GA9/B×-2-2-2-2-3
How do you play an A 9th chord on guitar?
A 9th is played at the 4th fret as 5 4 5 4 5 ×: barre your index finger across fret 4, middle finger on the low E string at fret 5, ring finger on the D string at fret 5 and pinky finger on the B string at fret 5. The high e string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 5 | 2 | A (1) |
| 5 (A) | 4 | 1 (barre) | C♯ (3) |
| 4 (D) | 5 | 3 | G (♭7) |
| 3 (G) | 4 | 1 (barre) | B (2) |
| 2 (B) | 5 | 4 | E (5) |
| 1 (e) | muted | — | — |
AdvancedThe index barre must fret the A string and the G string cleanly while the pinky reaches fret 5 on the B string.
5th fret
A 9th is played at the 5th fret as 5 7 5 6 5 7: barre your index finger across fret 5, ring finger on the A string at fret 7, middle finger on the G string at fret 6 and pinky finger on the high e string at fret 7.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 5 | 1 (barre) | A (1) |
| 5 (A) | 7 | 3 | E (5) |
| 4 (D) | 5 | 1 (barre) | G (♭7) |
| 3 (G) | 6 | 2 | C♯ (3) |
| 2 (B) | 5 | 1 (barre) | E (5) |
| 1 (e) | 7 | 4 | B (2) |
A9/C♯ inversion · fret 4
A 9th is played at the 4th fret as × 4 5 4 5 5: barre your index finger across fret 4, middle finger on the D string at fret 5, ring finger on the B string at fret 5 and pinky finger on the high e string at fret 5. The low E string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | muted | — | — |
| 5 (A) | 4 | 1 (barre) | C♯ (3) |
| 4 (D) | 5 | 2 | G (♭7) |
| 3 (G) | 4 | 1 (barre) | B (2) |
| 2 (B) | 5 | 3 | E (5) |
| 1 (e) | 5 | 4 | A (1) |
A9/C♯ inversion · fret 7
A 9th is played at the 7th fret as 9 7 7 9 8 7: barre your index finger across fret 7, ring finger on the low E string at fret 9, pinky finger on the G string at fret 9 and middle finger on the B string at fret 8.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 9 | 3 | C♯ (3) |
| 5 (A) | 7 | 1 (barre) | E (5) |
| 4 (D) | 7 | 1 (barre) | A (1) |
| 3 (G) | 9 | 4 | E (5) |
| 2 (B) | 8 | 2 | G (♭7) |
| 1 (e) | 7 | 1 (barre) | B (2) |
A9/C♯ inversion · fret 9
A 9th is played at the 9th fret as 9 10 9 9 10 9: barre your index finger across fret 9, ring finger on the A string at fret 10 and pinky finger on the B string at fret 10.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 9 | 1 (barre) | C♯ (3) |
| 5 (A) | 10 | 3 | G (♭7) |
| 4 (D) | 9 | 1 (barre) | B (2) |
| 3 (G) | 9 | 1 (barre) | E (5) |
| 2 (B) | 10 | 4 | A (1) |
| 1 (e) | 9 | 1 (barre) | C♯ (3) |
Why it sounds like that
A 9th stacks a major triad (1, 3, 5) with a minor seventh and a major ninth: 1, 3, 5, ♭7, 9. The ♭7–9 combination gives the chord its dominant pull. Compare it with A 7th, which stops at the ♭7 and sounds less colourful.
What goes wrong with A 9th?
- Letting the index barre collapse so the G string buzzes at fret 4.
- Allowing the high e string to ring open, which adds an unwanted E above the chord.
- Placing the ring finger on the G string instead of the D string, losing the fifth.
When to use it
A 9th works as the dominant in D major, where it can replace A major in progressions like D–G–A–D (I–IV–V–I). It suits blues, funk and jazz-rock comping.
Changing to and from A 9th
- Move to G 9th by sliding the shape down two frets to the 2nd fret.
- Move to B♭ 9th by sliding the shape up one fret to the 5th fret.
Which voicing to use
The 4th fret and 5th fret voicings both put A in the bass, but the 5th fret version adds the ninth on top for a brighter sound. Use the A9/C♯ inversion when you want the third in the bass for a smoother voice-leading.
Other A chords
Common questions
How is A 9th written?
A 9th is written as A9. The symbol A9 always means a dominant ninth chord with a minor seventh and a major ninth.
What is the difference between A 9th and A add 9?
A 9th includes the minor seventh G, while A add 9 is a plain A major triad with the ninth B added and no seventh. The add 9 sounds more open and less bluesy.
Why does the A9/C♯ inversion have a different bass note?
The A9/C♯ inversion places the third, C♯, in the bass instead of the root A. This creates a smoother stepwise bass line when moving between chords in D major.