Ab7#9 guitar chord
The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
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About Ab7#9 — drop 3 voicings
Ab7#9 is Ab, C, Eb, Gb and B — Ab9 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.
Ab7#9 notes and formula
| Ab | C | Eb | Gb | B |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♯9 |
Altered dominant — dominant function with a blues third on top.
Also written Ab7(#9), Ab7+9 or Ab7♯9. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play Ab7#9
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
Ab7#9 has 9 of them, on strings 5-3-2-1 and strings 6-4-3-2, from open position up to the 13th — every inversion the chord has: Ab in the bass, C in the bass, Gb in the bass and B in the bass. The one to learn first is the B shape at the nut.
5 of them sit on strings 5-3-2-1, 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 xx6577 — no barre and low, at the 5th fret. None of the shapes for Ab7#9 uses an open string, so every one of them is movable; the lowest sits at the 1st fret. 4 of the 8 need a barre. Together they cover the neck from the 1st fret to the 12th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x21112 | 1st fret | B, 9th in the bass | Gb | barred |
| 4344xx | 3rd fret | Ab, root position | B | barred |
| x34444 | 3rd fret | C, 1st inversion | Ab | barred |
| 464577 | 4th fret | Ab, root position | B | all fretted |
| 464547 | 4th fret | Ab, root position | B | barred |
| xx6577 | 5th fret | Ab, root position | B | all fretted |
| x66577 | 5th fret | Eb, 2nd inversion | B | all fretted |
| x-11-10-11-12-x | 10th fret | Ab, root position | B | all fretted |
The same notes rebuilt from scratch give 3 shell, 12 drop 2, 12 rootless and 5 open string voicings, each on its own page.
Tensions. A shell of Ab7#9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (D), the b13 (Fb) and the 13 (F).
How to use Ab7#9
Ab7#9 is a dominant with its tension raised, so it still points at Db — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
What to play over Ab7#9
Every note of Ab7#9 is in Ab half-whole diminished.
Chords near Ab7#9
Change one note of Ab7#9 and you have Abm7 (drop the major third), Abm9 (the major third becomes a ninth), Ab7 (drop the minor third), Ab9 (the minor third becomes a ninth) or Ab7b9 (the minor third becomes a flat ninth).
Ab7#9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On Ab7#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.