A9 Chord on Guitar
A9 = A – C# – E – G – B (Root, Major 3rd, Perfect 5th, Minor 7th, Major 9th)
A9 is a dominant chord — a full dominant seventh with a ninth stacked above it — fretted at the fifth-fret barre position, the same low spot on the neck as A major itself. It's built from the standard reduced guitar voicing that drops the fifth, since fitting all five notes of a real 9th chord across six strings isn't physically possible without doubling.
The full harmonic content is A, C#, E, G, B: root, major third, fifth, flat seventh, and ninth. Functioning as V9, A9 pulls strongly toward D major, one of the guitar's easiest and most frequently used open-position keys, so this exact barre shape is the natural dominant chord for anyone playing in D. That dominant pull — driven mainly by the C#-to-D half step and the G-to-... resolution downward — is what makes A9 feel unsettled compared to a plain A major triad in the same spot.
Fingerings
Barre (5th fret)
How to Practice It
Compare A9 directly against plain A major and A7 at the same fret to hear how each extra note thickens the tension before a D-major resolution; alternating A – A7 – A9 – D is a useful ear-training loop. Since the barre position is identical to A major, this is also a good chord for practicing clean addition of the extra fretted notes without disturbing the barre itself, a skill that transfers to every other dominant 9th shape on the neck.
Common Progressions
- A9 – D (V9 – I in D major)
- D – A9 – D (I – V9 – I)
- Em – A9 – D (ii – V9 – I in D major)
- A9 – D – G – D (V9 – I – IV – I)
FAQ
- What notes make up A9?
- A, C#, E, G, and B — root, major third, fifth, flat seventh, and ninth — though the guitar voicing used here drops the fifth to keep the shape playable across six strings.
- How does A9 differ from A add9?
- A9 includes the flat seventh (G) along with the ninth, giving it a dominant, tension-seeking quality, while A add9 keeps the plain major triad and simply adds the ninth on top without any seventh at all.
- Why is A9 especially useful for guitarists?
- It's the dominant chord of D major, arguably the guitar's most comfortable open-position key, so A9 shows up constantly as the chord right before a D resolution in folk, pop, and rock material written in D.
- Is A9 harder to finger than plain A7?
- Slightly — it asks for one more fretted note on top of the A7 shape at the same fifth-fret barre, but since the position and barre are unchanged, most players who have A7 solid can add the ninth with a little extra stretch.
- Does A9 always resolve to D major?
- Not always, but that's its strongest and most common pull as a V9 chord; it can also function as a secondary dominant briefly tonicizing D minor, or simply sit as a colorful dominant sonority without resolving at all in more modal or vamp-based writing.
- Why does the guitar voicing of A9 drop the fifth?
- A five-note chord doesn't fit cleanly across six strings without either doubling a note or muting one, and the fifth is the least essential tone for identifying the chord's quality, so guitarists routinely omit it in favor of keeping the root, third, seventh, and ninth intact.
- What's a quick way to hear A9's tension resolve?
- Play A9 for a full bar and then land on D major — the ninth and flat seventh both want to fall by step, and hearing them settle into D's plain major triad is one of the clearest small demonstrations of dominant resolution available on the guitar.
- Is A9 ever used as a I chord rather than a V chord?
- In funk, blues, and soul-influenced writing, yes — a dominant 9th built on the tonic itself is a common way to color an otherwise plain major-key vamp, treating the chord as a stable groove sound rather than a chord that must resolve anywhere.
A9 on other instruments: A9 on Piano. Related: how chords are built, chord finder.