The open chord
Frets, low E to high E: x 0 2 2 2 0 — notes x A E A C# E. The root is the open A string.
| String | Fret | Note | Role |
|---|---|---|---|
| 1 (high E) | 0 | E | 5th |
| 2 (B) | 2 | C# | 3rd |
| 3 (G) | 2 | A | root (octave) |
| 4 (D) | 2 | E | 5th |
| 5 (A) | 0 | A | root |
| 6 (low E) | x | — | muted |
As a movable (barre) shape
Barre the 5th–1st strings at fret N with your index finger. Your other fingers fret the three middle strings two frets above the barre. The root is on the A string at fret N.
Example — C major as an A-shape at the 3rd fret:
| String | Fret | Note | Role |
|---|---|---|---|
| 1 (high E) | 3 (barre) | G | 5th |
| 2 (B) | 5 | E | 3rd |
| 3 (G) | 5 | C | root (octave) |
| 4 (D) | 5 | G | 5th |
| 5 (A) | 3 (barre) | C | root |
| 6 (low E) | x | — | muted |
Shortcut: place the barre at the fret whose A-string note is your target root, then add the 2-fret-above "A triangle" on the D, G, and B strings.
Where it sits on the neck
The A-shape sits between the C-shape (below) and the G-shape (above) for a given chord. For C major, the C-shape is in open position, the A-shape appears at the 3rd fret, and the G-shape starts around the 3rd–7th frets with its root on the low E string at the 8th fret.
Common variants
Am-shape (minor)
Move the 3rd on the B string down one fret. The open Am is x 0 2 2 1 0; as a movable barre it becomes the familiar 5th-string-root minor shape.
A7-shape (dominant 7th)
Open A7 is x 0 2 0 2 0 — the G string drops to the open (b7). As a movable shape this becomes the standard "A-form 7" barre chord.
Amaj7-shape
Open Amaj7 is x 0 2 1 2 0 — the G string drops one fret to sound G# (the major 7th). A very common jazz voicing when moved up.