A7

A7 is A, C#, E and G, a dominant seventh. The shape this page opens on is written x02020, lowest string first.

Also written Adom7 or A dominant 7. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 9 common shapes for A7 on the guitar, and 36 derived voicings in 4 families.

In which keys. Every note of A7 belongs to D major (the V) and B minor (the ♭VII).

The common shapes, written lowest string first: x02020, x02223, xx2223, 542223, 575655, x07989, xx7989, x-12-11-12-10-x, x-12-14-12-14-12.

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. A7 has 545xxx, x056xx, x-12-11-12-x-x, x0x02x, 5x56xx, x-12-x-12-14-x.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. A7 has xx2223, 3422xx, x0202x, xx5655, 5756xx, x7768x, xx7989, x-10-11-9-10-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. A7 has x4x253, 3x222x, x0x020, x7x685, 5x565x, 9x798x, x-10-x-9-10-9, 12-x-11-12-10-x.

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. A7 has 545000, 57560x, 5x5600, 34220x, x05600, 04400x.

Tensions. A shell of A7, root, third and seventh, leaves a string free, and the tones that belong over it are the b9 (Bb), the 9 (B), the #9 (B#), 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.