A dominant ninth (A9) chord on piano

Dominant ninth chord (a dominant seventh plus a major ninth) on A: the notes of the A9 chord are A – C♯ – E – G – B.

Full chord: A3 – C♯4 – E4 – G4 – B4

What the A9 chord sounds like

A dominant ninth is a dominant seventh with an added major ninth. A fuller, fatter dominant sound – a staple of funk, soul and blues.

Notes of the A9 chord

Degree	Note	Interval from the root
1	A	root
3	C♯	major third (4 semitones)
5	E	perfect fifth (7 semitones)
7	G	minor seventh (10 semitones)
9	B	major second (2 semitones)

Piano voicings

Chords with five or more notes are rarely played in one hand: the left hand takes the root, the right hand the colour notes. The fifth (and in an eleventh chord the third) is often left out.

Full chord

A3 – C♯4 – E4 – G4 – B4

Two-hand voicing

A2 – C♯4 – G4 – B4 – E5

Which keys is it in?

The A9 chord is built from the notes of these keys (for minor keys, both the natural and the harmonic minor are considered):

D major: V9 (dominant)
B minor: VII9

Similar chords and substitutes

If A9 is too hard, or you want a different colour in the same spot, these chords are worth a try.

Substitutes (by function)

E♭7 – tritone substitute: the same third and seventh, swapped – a jazz favourite
C♯dim7 – diminished seventh on the third: a common stand-in for the dominant
A7 – a simpler dominant
A7sus4 – suspended dominant, less tense
D – where it resolves (V → I)

Simpler versions

A7 – all 4 of its notes are in this chord
Aadd9 – all 4 of its notes are in this chord
A – all 3 of its notes are in this chord
Asus2 – all 3 of its notes are in this chord

Richer versions

A11 – the same chord plus 1 colour note
A13 – the same chord plus 1 colour note

Frequently asked questions

What notes are in the A9 chord?

A, C♯, E, G, B. The root is A; the intervals of the other notes from the root: major third, perfect fifth, minor seventh, major second.

How do I play the A9 chord on piano?

Play the root with your left hand and the colour notes (third, seventh, ninth) with your right hand – the two-hand voicing above. Stacking all 5 notes in one hand is possible but sounds crowded.

How is the A9 chord written?

The chord symbol is A9, and its full name is A dominant ninth.