A Dominant 9th Chord: Notes, Voicings, and How to Play It

One finger on the fourth string at the 2nd fret, everything else left open, and five strings sound A, E, G and B. That is four of the five notes of A9 for free at the nut, x 0 2 0 0 0. The missing one is C♯, the third, the note that makes the chord a dominant rather than a modal drone, and buying it back costs three more fingers and both open strings that made the trick work.

Try It: A9 in the Chord Finder

Sound A7, then put a B above it and listen to the chord turn glossy without losing its lean.

The Notes of A9

Written out: A, C♯, E, G, B. Four white keys, one black, fourteen semitones from bottom to top, and one note more than most hands and guitar grips care to carry. Real voicings leave something out, usually the E or the A; the guide to extended chords sets out the order in which notes go.

How A9 Is Built

Take A7, which is A, C♯, E and G, and stack a B on top. The chord keeps its single point of tension: C♯ up to G is six semitones, and no other pair in it comes near a tritone.

What the B brings is the opposite of tension. It sits a perfect 5th above the E and a major 3rd above the G, which makes E, G and B an ordinary E minor triad. A9 is a consonant triad balanced on a tritone, harder than it sounds and sweeter than it should be.

That tritone still knows where it is going. C♯ is a semitone under D, G a semitone over F♯, and moving both lands the music on D major. The A and the B need not move at all, arriving as the root and the 6th of D6.

Drop the G and the remaining A, C♯, E and B are Aadd9, which keeps the added note but loses both the seventh and the tritone with it.

What Is Left When the Root Goes

Take the A away and C♯, E, G, B is a chord in its own right, the C♯ half-diminished seventh in root position. A bass player holding A while a pianist plays C♯m7♭5 produces A9 between them, with nobody voicing all of it.

Take the third away as well and E, G and B is the E minor triad again, the shortcut most guitarists use without naming it.

A9 on the Piano

One black key in five decides the fingering. Set the right hand on C♯, E, G and B and the thumb lands on the raised key, set back into the keyboard where a thumb has least reach. Rotate the same four notes to G, B, C♯, E and the black key moves under the second or third finger, the outer fingers on white keys near the front edge. That is why most players learn this chord in that order rather than from the third upward.

Both shapes are rootless, the usual arrangement: A2 alone in the left hand, four notes in the right. If the left hand wants a second note, take the G a minor 7th above it rather than the C♯, since down there a major 3rd thickens and a 7th stays clear.

Three notes will do if the texture is busy. Drop the E and what remains, C♯, G and B, fits under the thumb, index and little finger with the tritone at the bottom and the ninth on top. As far as a listener is concerned that is the chord.

A9 on the Guitar

Follow the opening trick through and you can watch the chord unravel. x 0 2 0 0 0 hands you A, E, G and B, the G on the open third string sitting directly below the B on the open second. Fret the second string at the 2nd fret for the C♯ and the free B is gone. Its nearest replacement is the third string at the 4th fret, so the free G goes too, and the only G left within reach is the first string at the 3rd fret, above everything.

The seventh and the ninth have swapped ends. The complete open voicing is x 0 2 4 2 3, sounding A2, E3, B3, C♯4 and G4, and it asks one finger to reach across another to a lower string at a higher fret. That crossing is why almost nobody plays A9 at the nut, however tempting the open strings look.

Guitarists take it up the neck instead, to the E9 shape barred at the 5th fret, 5 7 5 6 5 7. All five notes are there with the root in the bass, and the top four strings of it, x x 5 6 5 7, are the grip most people mean when they say a ninth chord: flattened 7th, 3rd, 5th and 9th, no root, four adjacent strings, easy to choke between strums. Higher up, x 12 11 12 12 x drops the E and rebuilds the chord on the fifth string.

A blues in A ends up at the fifth fret as a result. A9 is at 5 7 5 6 5 7, D9 at x 5 4 5 5 x and E9 at x 7 6 7 7 x, so all three chords of the twelve bar sit between the 4th and 7th frets and the hand barely travels. None uses an open string, which is what a rhythm player wants here: every note stops dead when the fingers relax.

Inversions

Five notes give four inversions, and most are theory rather than practice, since the fifth usually leaves before anyone gets that far. What players rotate is C♯, E, G and B, choosing whichever order puts the C♯ and the G in the middle voices when D is coming next, so those two can close inward while the B holds still.

The bottom row is the one to leave alone. With B underneath, the A above it reads as a flattened 7th and the G as a flattened 13th, which earns the chord a name nobody wants on a chart. Treat that B as a passing bass note.

Voicings

Which Keys Contain A9

• V of D major
• VII of B natural minor
• IV of E dorian
• I of A mixolydian
• II of G lydian
• V of D melodic minor

The first five are one scale wearing five names. D major, B natural minor, E dorian, A mixolydian and G lydian hold the same seven notes, so the list is shorter than it looks: this chord wants a C♯ and a G natural at once, and that pair points at one collection.

D melodic minor is the genuine outsider, and it settles a question minor keys keep asking. Its sixth degree is a B natural, so its dominant takes a natural 9th and A9 fits. D harmonic minor has a B♭ there instead and its dominant comes out as A7♭9. Choose this chord for a cadence into D minor and you have quietly chosen the melodic form of the scale.

Where A9 Shows Up

The second row hides how little work it takes. Em7 is E, G, B and D, and three of those notes are already in A9. Only the D leaves and only the A and the C♯ arrive, so the ii to V move barely disturbs the voicing. That is also why an E minor shape thrown over an A bass sounds right before the third is even added.

The vamp in the third row is the same relationship refusing to go anywhere. E dorian takes Em7 as its tonic and A9 as its IV, and since neither chord needs the other a band can rock between them for as long as it likes. This chord suits that job because its tension is one interval buried under a consonant triad, so it never sounds as though it is waiting for permission.

The blues row is geography more than harmony. All three chords are the same grip at different frets, so a rhythm player learns one shape and one wrist movement and covers the form. That is much of why the ninth rather than the plain seventh became the sound of funk and soul guitar in this key.

Related Chords

• A Dominant 7th Chord the four notes this is built on
• A Add9 Chord the same added B with no seventh under it
• C♯ Half-diminished Chord what is left when the root is taken away
• E Minor 7th Chord three notes in common, and the chord in front of it in a ii, V
• Seventh Chords: The Complete Guide

Learn More

• Extended Chords: Which Tensions Work, and How to Voice Them
• The ii, V, I Progression in Practice
• Chord Inversions and Voice Leading
• The Circle of Fifths Explained
• The A Mixolydian Scale