A7b9

A7b9 is A, C#, E, G and Bb, a seven flat nine. The shape this page opens on is written x02323, lowest string first.

Also written A7(b9), A7-9 or A7♭9. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 6 common shapes for A7b9 on the guitar, and 44 derived voicings in 5 families.

The common shapes, written lowest string first: x02323, 5453xx, xx5656, 575656, xx7686, x-12-11-12-11-12.

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. A7b9 has 5453xx, xx7686, x-12-11-12-11-x, x0x026.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. A7b9 has 5453xx, xx7686, x-12-11-12-11-x, x1522x, xx5325, 6-10-7-6-x-x, x-10-8-6-10-x, 9-12-8-12-x-x.

Drop 3. The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped. A7b9 has x1x223, 5x532x, 6x768x, x-10-x-6-10-6, 9-x-8-12-10-x, x-12-x-12-11-9, 15-x-11-14-11-x, x-13-x-14-14-15.

Rootless. The root left to the bass player. Frees a finger for a tension. A7b9 has x1202x, xx2323, x4535x, xx5656, x7868x, xx8989, x-10-11-9-11-x, x-x-11-12-11-12.

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. A7b9 has x02323, 5x5320, 005656, 0x5325.

Tensions. A shell of A7b9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (D#), 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.