Ab7b5 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 Ab7b5 — drop 3 voicings
Ab7b5 is Ab, C, D and Gb — Ab7 with the fifth lowered a semitone.
It sounds symmetrical and slightly unreal. The same four notes spell a 7♭5 a tritone away, which is exactly why one can stand in for the other.
Altered dominant — and the chord that makes the tritone substitution work.
Ab7b5 notes and formula
| Ab | C | D | Gb |
|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 |
Also written Ab7(b5), Ab7-5 or Ab7♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play Ab7b5
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.
Ab7b5 has 10 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, Ebb in the bass and Gb in the bass. The one to learn first is the C 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.
Play Ab7b5 as a shell — root, third and seventh — and the spare string takes the b9 (Bbb), the 9 (Bb), the #9 (B), the b13 (Fb) or the 13 (F).
All 5 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
- 4x453x, 3rd fret, Ab, root position, top note D, all fretted
- xx6778, 6th fret, Ab, root position, top note C, all fretted
- x-9-10-11-9-10, 9th fret, Gb, 3rd inversion, top note D, all fretted
- x-x-10-11-9-10, 9th fret, C, 1st inversion, top note D, all fretted
- x-11-12-11-13-x, 11th fret, Ab, root position, top note C, all fretted
How to use Ab7b5
Ab7b5 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 Ab7b5
Every note of Ab7b5 is in Ab whole tone, Ab lydian dominant, Ab altered and Ab half-whole diminished.
Chords near Ab7b5
Change one note of Ab7b5 and you have Abmaj7b5 (the flat seventh becomes the major seventh), Abm7b5 (the major third becomes the minor third), Ab7 (the flat fifth becomes the fifth), Abaug7 (the flat fifth becomes the sharp fifth) or Ab9b5 (add the ninth).
Ab7b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.