A9

A9 is A, C#, E, G and B, a dominant ninth. The shape this page opens on is written x22223, lowest string first.

Also written Adom9 or A dominant 9. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 10 common shapes for A9 on the guitar, and 45 derived voicings in 5 families.

In which keys. Every note of A9 belongs to D major (the V) and B minor (the ♭VII).

The common shapes, written lowest string first: x22223, x02423, 542000, 522423, 5454xx, 575457, 575657, xx7687, 9x7987, x-12-11-12-12-12.

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. A9 has 5454xx, xx7687, x-12-11-12-12-x, x0x027.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. A9 has 5454xx, xx7687, x-12-11-12-12-x, x2522x, xx5425, x4748x, 7-10-7-6-x-x, x-10-9-6-10-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. A9 has x2x223, 5x542x, x4x485, 7x768x, x-10-x-6-10-7, x-12-x-12-12-9, 9-x-9-12-10-x, 15-x-11-14-12-x.

Rootless. The root left to the bass player. Frees a finger for a tension. A9 has x2202x, xx2423, x4545x, xx5657, xx9989, x-x-11-12-12-12, x-14-14-12-14-x, x2x020.

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. A9 has 545400, x02423, 5x5420, 005657, 02522x, x25220.

Tensions. A shell of A9, 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.