Ab9b5 guitar chord
An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful.
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About Ab9b5 — open string voicings
Ab9b5 is Ab, C, D, Gb and Bb — Ab7b5 with the natural ninth added over it.
It sounds sleek and tense. Played as a tritone substitution the ♭5 is the root of the dominant it replaced.
Ab9b5 notes and formula
| Ab | C | D | Gb | Bb |
|---|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 | 9 |
Altered dominant — commonly the tritone substitute.
Also written Ab9(b5), Ab9-5 or Ab9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play Ab9b5
An open string left ringing against a fretted grip. It costs no finger, so it can sound a note the closed shape has none left for: a tension on top, or a pedal root underneath.
These belong to their key rather than to a shape: they cannot be moved up the neck. D, A, G and E have many; E♭ has a handful.
Ab9b5 has 1 of them, only on strings 5-4-3-2-1, all of them at the 3rd fret — all in one inversion, so the bass note never moves. The one to learn first is the C shape at the 3rd fret, which is the easiest grip here.
Start with 4303x2 — no barre and 1 open string. 1 of the 5 shapes here sits in open position. 2 of the 5 need a barre. Together they cover the neck from the 2nd fret to the 11th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| 434334 | 3rd fret | Ab, root position | Ab | barred |
| 4303x2 | open position | Ab, root position | Gb | 1 open string |
| 4545x6 | 4th fret | Ab, root position | Bb | all fretted |
| x56576 | 5th fret | Ebb, 2nd inversion | Bb | all fretted |
| x-11-10-11-11-10 | 10th fret | Ab, root position | D | barred |
The same notes rebuilt from scratch give 8 shell and 14 rootless voicings, each on its own page.
Tensions. A shell of Ab9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (Fb) and the 13 (F).
How to use Ab9b5
Ab9b5 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 Ab9b5
Every note of Ab9b5 is in Ab whole tone and Ab lydian dominant.
Chords near Ab9b5
Change one note of Ab9b5 and you have Ab7b5 (drop the ninth), Ab9 (the flat fifth becomes a fifth), Abaug9 (the flat fifth becomes a sharp fifth) or Ab9#11 (add the fifth).
Ab9b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On Ab9b5’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.