A7#9 guitar chord
A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings.
- Tap a note to hear it
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- Fingers, notes or intervals
- Play the chord
About A7#9 — drop 2 voicings
A7#9 is A, C#, E, G and B# — A9 with the ninth raised a semitone.
It sounds gritty and contradictory. The minor third sounding over the major third; every guitarist knows it as the Hendrix chord.
A7#9 notes and formula
| A | C# | E | G | B# |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♯9 |
Altered dominant — dominant function with a blues third on top.
Also written A7(#9), A7+9 or A7♯9. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play A7#9
Take the four notes stacked as close together as they go, then drop the second voice from the top an octave. The gap it opens is what makes the chord sound like a chord rather than a cluster.
It lands on four adjacent strings, which is why it is the workhorse voicing on guitar.
A7#9 has 12 of them, on the bottom four strings, the top four strings and the middle four strings, from the 2nd fret up to the 11th — every inversion the chord has: A in the bass, C# in the bass, G in the bass and B# in the bass. The one to learn first is the A shape at the 4th fret, which is the easiest grip here.
4 of them sit on the bottom four strings, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Start with xx7688 — no barre. None of the shapes for A7#9 uses an open string, so every one of them is movable; the lowest sits at the 2nd fret. 4 of the 9 need a barre. Together they cover the neck from the 2nd fret to the 13th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x32223 | 2nd fret | B#, 9th in the bass | G | barred |
| 5455xx | 4th fret | A, root position | B# | barred |
| x45555 | 4th fret | C#, 1st inversion | A | barred |
| 575688 | 5th fret | A, root position | B# | all fretted |
| 575658 | 5th fret | A, root position | B# | barred |
| xx7688 | 6th fret | A, root position | B# | all fretted |
| x77688 | 6th fret | E, 2nd inversion | B# | all fretted |
| x-0-10-9-8-9 | 8th fret | A, root position | C# | 1 open string |
| x-12-11-12-13-x | 11th fret | A, root position | B# | all fretted |
The same notes rebuilt from scratch give 3 shell, 9 drop 3, 14 rootless and 5 open string voicings, each on its own page.
Tensions. A shell of A7#9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (D#), the b13 (F) and the 13 (F#).
How to use A7#9
A7#9 is a dominant with its tension raised, so it still points at D — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Voice by voice, A7#9 → D. 2 voices move by a semitone, and one note is common to both chords.
| In A7#9 | Moves | In D |
|---|---|---|
| A, the root | stays where it is | A, the fifth |
| C#, the major third | rises a semitone | D, the root |
| E, the fifth | falls a whole tone | D, the root |
| G, the flat seventh | falls a semitone | F#, the major third |
| B#, the sharp ninth | rises a whole tone | D, the root |
What to play over A7#9
Every note of A7#9 is in A half-whole diminished.
Chords near A7#9
Change one note of A7#9 and you have Am7 (drop the major third), Am9 (the major third becomes a ninth), A7 (drop the minor third), A9 (the minor third becomes a ninth), A7b9 (the minor third becomes a flat ninth) or A/G (drop the minor third).
A7#9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On A7#9’s sound and use this page follows Mark Levine, The Jazz Theory Book (Sher Music, 1995). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.