Abm7b5 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 Abm7b5 — drop 3 voicings
Abm7b5 is Ab, Cb, D and Gb — Abm7 with the fifth lowered a semitone.
It sounds hollow, and unmistakably going somewhere. Almost always the first chord of a minor ii–V–i, so it walks straight into an altered dominant.
Abm7b5 notes and formula
| Ab | Cb | D | Gb |
|---|---|---|---|
| 1 | ♭3 | ♭5 | ♭7 |
Pre-dominant — the ii of a minor key.
Also written Abø, Abø7, Abm7-5, Abm7(b5) or Ab half diminished. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play Abm7b5
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.
Abm7b5 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, Cb in the bass, Ebb in the bass and Gb in the bass. The one to learn first is the Cb 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 xx0102 — no barre and 2 open strings. 1 of the 8 shapes here sits in open position. 3 of the 8 need a barre. Together they cover the neck from the 1st fret to the 14th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| xx0102 | open position | Ebb, 2nd inversion | Gb | 2 open strings |
| 4x443x | 3rd fret | Ab, root position | D | barred |
| 4xx432 | 2nd fret | Ab, root position | Gb | all fretted |
| 456474 | 4th fret | Ab, root position | Ab | barred |
| xx6777 | 6th fret | Ab, root position | Cb | barred |
| x-11-9-11-9-10 | 9th fret | Ab, root position | D | all fretted |
| x-11-12-11-12-x | 11th fret | Ab, root position | Cb | all fretted |
| x-x-12-13-12-14 | 12th fret | Ebb, 2nd inversion | Gb | all fretted |
The same notes rebuilt from scratch give 4 shell, 14 drop 2 and 6 open string voicings, each on its own page.
Tensions. A shell of Abm7b5, root, third and seventh, leaves a string free, and the tones that belong over it are the 11 (Db) and the b13 (Fb).
How to use Abm7b5
Abm7b5 is the ii of Gb minor, which is where it is nearly always found: half-diminished, then an altered dominant, then the minor tonic.
In which keys. Every note of Abm7b5 belongs to F# minor (the ii°, the supertonic) and A major (the vii°, the leading tone).
What to play over Abm7b5
Every note of Abm7b5 is in Ab blues, Ab locrian, Ab altered and Ab half-whole diminished.
Chords near Abm7b5
Change one note of Abm7b5 and you have Abdim (drop the flat seventh), Abdim7 (the flat seventh becomes a sixth), Abm7 (the flat fifth becomes a fifth), AbmMaj7b5 (the flat seventh becomes a major seventh) or Ab7b5 (the minor third becomes a major third).
Abm7b5 is a diminished chord — root, minor third, flat fifth. Diminished and half-diminished chords on every root.
On Abm7b5’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.