Abm7b5

Abm7b5 is Ab, Cb, D and Gb, a half-diminished seventh. The shape this page opens on is written xx0102, lowest string first.

Note by note. Ab is the root, Cb is the minor third, D is the flat fifth and Gb is the flat seventh.

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.

There are 8 common shapes for Abm7b5 on the guitar, and 34 derived voicings in 4 families.

One note away. Change a single note of Abm7b5 and you have Abdim (with one note taken away), Abdim7 (with one note moved), Abm7 (with one note moved), AbmMaj7b5 (with one note moved) or Ab7b5 (with one note moved).

In which keys. Every note of Abm7b5 belongs to F# minor (the ii°) and A major (the vii°).

The common shapes, written lowest string first: xx0102, 4x443x, 4xx432, 456474, xx6777, x-11-9-11-9-10, x-11-12-11-12-x, x-x-12-13-12-14.

Under the hand. 1 of the 8 shapes here sits in open position, and the first uses 2 open strings with 2 left unplayed. 3 of the 8 need a barre. Together they cover the neck from the 1st fret to the 14th.

Where it goes. 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.

Shell. 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. Abm7b5 has 4x443x, x-11-x-11-12-10, 4247xx, 4997xx.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. Abm7b5 has xx0102, 2201xx, xx4434, 4544xx, xx6777, x9979x, 10-11-9-11-x-x, x-x-9-11-9-10.

Drop 3. The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped. Abm7b5 has x2x132, 2x010x, 4x443x, x5x474, 7x677x, x9x797, 10-x-9-11-9-x, x-11-x-11-12-10.

Open string. 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. Abm7b5 has 454400, 4x4430, 7x6770, x56470, 2x0400, xx0470.

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).

What kind of chord this is. Abm7b5 is a diminished chord — root, minor third, flat fifth. diminished and half-diminished chords on every root, and what they are for.

The common shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.