A7 chord on guitar
The A7 chord, or A dominant 7th, stacks 4 notes on A: A, C♯, E and G. Musicians write its formula 1 3 5 ♭7.
Notes and intervals of A7
Each note of A7 has a job. Counted from the root, you get root (A), major 3rd (C♯), perfect 5th (E) and minor 7th (G). Change one of these intervals and you get a different chord, which is why the formula 1 3 5 ♭7 is worth memorising rather than the shape alone.
| Degree | Interval | Note |
|---|---|---|
| 1 | root | A |
| 3 | major 3rd | C♯ |
| 5 | perfect 5th | E |
| ♭7 | minor 7th | G |
How to play A7 on guitar
Start with the first diagram: x 0 2 0 2 0, read from the 6th string (low E) to the 1st string (high E). Your lowest note is A. The next positions give the same notes in a different order, which is useful when you want A7 to sit closer to the surrounding chords.
Let the open strings ring: strum slowly once and check that every note sounds clean before you speed up.
Which keys use A7?
You find A7 as a diatonic chord in D major (V7). The most common case is D major, where it plays the role of V7.
Scales to play over A7
These scales share every note of A7: A Mixolydian mode. A Mixolydian mode is the safest choice; the others add more colour.
About dominant 7th chords
A major triad plus a minor seventh: 1 3 5 ♭7. The third and the seventh form a tritone, the unstable interval that wants to resolve, which gives the dominant seventh its tension and its bluesy edge. On its own it sounds unfinished; followed by the chord a fifth below, it sounds like an arrival. For example C7: C E G B♭.
Its main job is V7 to I, the strongest cadence in tonal music (for example G7 to C). It also works as a secondary dominant: V7 of V, V7 of vi and so on. In the blues every chord can be a 7, I7 IV7 V7 for the whole 12-bar form, and jazz uses it in ii7 V7 Imaj7.
Open shapes such as E7, A7, D7, G7, C7 and B7 come first. The movable ones come from the barre chords: the E-shape 7 (♭7 on the 4th string) and the A-shape 7 (♭7 on the 3rd string). For blues and jazz, three-note shells (root, 3, ♭7) with the root on the 6th or 5th string are very handy.
The big one: 7 is not maj7. A plain 7 always means a minor seventh (B♭ in C7), maj7 means a major seventh (B in Cmaj7), and the two sound opposite, tense versus calm. Also, inside a major key only the V chord is naturally a dominant 7; elsewhere it is a borrowed colour or a secondary dominant.
Frequently asked questions
What notes are in the A7 chord?
A7 (A dominant 7th) contains A, C♯, E and G. In intervals: root (A), major 3rd (C♯), perfect 5th (E) and minor 7th (G).
How do you play A7 on guitar?
The easiest shape is x 0 2 0 2 0, from the low E string to the high E string. This page shows 3 positions with finger numbers.
What scale goes with A7?
A Mixolydian mode fits A7 best. Other scales that contain all its notes: A Mixolydian mode.
What key is A7 in?
A7 belongs to D major (V7). In D major it is the V7 chord.
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