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The A9 chord

The A9 (A - C# - E - G - B) is a dominant ninth, which is why it sounds a seventh chord with an extra layer of colour. Writers pick it for a strong cadence into the next chord, and you can find it across the twelve-bar blues and gospel turnarounds. On guitar the chord sits easily under standard open chord shapes; on piano it stacks straight up under the right hand. The page below covers the voicings worth memorising, the theory, the progressions where the A9 earns its keep, and the records that lean on it.

Hear the A9 in the chord builder →

Voicings for A9

Common ways to grip the A9 on guitar and piano. Guitar diagrams read low E to high E left-to-right; an × means muted, an open circle above the nut means an open string. Filled dots are fretted notes.

Guitar , full chord shapes

CAGED-derived voicings for A9 across the neck. Pick the shape closest to where your hand already sits.

Guitar: E9 shape at fr.5

Notes: A - C# - E - G - B (chord tones)

Guitar: 9th shape at fr.11

Notes: A - C# - E - G - B (chord tones)

Guitar , triad shapes

Three-note triad shapes on each string set, shown moving up the neck. Light textures for arpeggios, pop layering and chord-melody work.

Triad: top strings (G-B-e) · fr.2

Notes: top-string triad, fr.2

Triad: top strings (G-B-e) · fr.6

Notes: top-string triad, fr.6

Triad: top strings (G-B-e) · fr.9

Notes: top-string triad, fr.9

Triad: middle strings (D-G-B) · fr.2

Notes: middle-string triad, fr.2

Triad: middle strings (D-G-B) · fr.6

Notes: middle-string triad, fr.6

Triad: middle strings (D-G-B) · fr.11

Notes: middle-string triad, fr.11

Triad: bass strings (A-D-G) · fr.2

Notes: bass-side triad, fr.2

Triad: bass strings (A-D-G) · fr.4

Notes: bass-side triad, fr.4

Triad: bass strings (A-D-G) · fr.6

Notes: bass-side triad, fr.6

Piano voicings

Root position and inversions. The bass note matters: each inversion changes how the chord sits under a melody.

Piano: root position

Notes: A - C# - E - G - B. Root A at the bottom. The classic stacked-thirds spelling of a dominant ninth.

Piano: first inversion

Notes: C# - E - G - B - A. C# at the bottom. Common in chord-melody, walking bass lines and gentler voicings.

Piano: second inversion

Notes: E - G - B - A - C#. E at the bottom. A floating, suspended feel often used in hymns and ballads.

Piano: third inversion

Notes: G - B - A - C# - E. G at the bottom. The seventh in the bass , a smooth jazz favourite.

The theory behind A9

A9 is a dominant ninth built on A. Its three or four notes (A - C# - E - G - B) sit a specific distance apart: root, major third, perfect fifth, minor seventh and major ninth. That makes it a passing chord in the key of a closely related major key, and the same chord works as the passing chord in a closely related major key. The simplest rule of thumb: the A9 wants to resolve down a fifth to the next chord.

Progressions that use A9

Short progressions that put the A9 to work. Each one is shown in a different key so you can pick the one that suits your singer.

I→IV→V key of C major

A9 (as passing colour)

This chord appears as a borrowed or passing chord in many major-key progressions.

→ Build this in the chord builder

Songs that feature A9

Real records where this chord does structural work. No lyrics quoted, just the title and artist so you can pull up a copy and hear it in context.

Related chords

Chords a step away from the A9 in the songwriting circle, the natural neighbours when you want a substitution.

TriadA DomA7 Maj7Amaj7 m7Am7 NeighbourE NeighbourEm NeighbourE7 NeighbourD

Keys where A9 lives

The keys where this chord turns up diatonically. Open any key page for the full set of progressions that lean on it.

C major A minor

Related references

Other ways to put the A9 to work across the reference library.

Arpeggiooutline it with arpeggios

More songwriting tools

Got the chord but still wrestling with the lyric? Find the right rhyme in RhymeForge, or break a writer's block with the unexpected word-pair generator in CollisionLab. Need to map a full progression? The chord builder on the home page is where the A9 fits into context. All free, no signup.

About the chord builder

The Undercover Zest chord progression builder is a free interactive tool that maps every diatonic and borrowed chord in every key. Click a Roman numeral to hear it, drag chords into a progression, then audition voicings, inversions and tensions until the song clicks.

This page is a static reference for the A9. For interactive playback, voice-leading hints and substitution suggestions, open the chord builder above.