A9b5

A9b5 is A, C#, Eb, G and B, a nine flat five. The shape this page opens on is written x01423, lowest string first.

Also written A9(b5), A9-5 or A9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 6 common shapes for A9b5 on the guitar, and 23 derived voicings in 3 families.

The common shapes, written lowest string first: x01423, 545445, 5656x7, x67687, x09889, x-12-11-12-12-11.

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. A9b5 has x0564x, 5454xx, xx7687, x-12-11-12-12-x, 5x564x, 5458xx, x-12-x-12-14-11, x0x027.

Rootless. The root left to the bass player. Frees a finger for a tension. A9b5 has x2102x, x4544x, xx9889, x-x-11-12-12-11, x-14-13-12-14-x, xx1423, x4x443, xx5647.

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. A9b5 has x05647.

Tensions. A shell of A9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (F) and the 13 (F#).

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