Ab9b5 guitar chord
Root, third and seventh: the guide tones fix the quality, so the fifth is dropped. That is what leaves a string free, so pick a tension to put on top.
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About Ab9b5 — shell 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
Root, third and seventh. The third and seventh, the guide tones, are what make the chord major, minor or dominant, so the fifth can go: it says nothing the symbol needs.
Three notes means a spare string, which is the real point. Put a tension on it.
Ab9b5 has 8 of them, on the bottom four strings, the top four strings, the middle four strings, strings 6-4-3-2 and strings 5-3-2-1, from the 3rd fret up to the 10th — all in one inversion, so the bass note never moves. The one to learn first is the Ab 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 14 rootless and 1 open string 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.