A Major 7th
maj7
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About A Major 7th
A major seventh is the A shape with one finger lifted: let the G♯ ring at the first fret of the G string and the chord appears. It is one of the two or three easiest major sevenths on the instrument, and it sounds like an unfinished sentence in the best sense.
The notes
A, C♯, E, G♯. The G♯ sits a semitone below the octave A — the half step that defines every major seventh and gives the chord its hovering quality.
Lower it to G and you have A7, which pulls toward D with real force. The two chords are one fret apart and belong to entirely different kinds of music.
On the fretboard
The common open shape frets the second fret on the D and B strings and the first on the G. It rings, and the open A and E strings fill it out.
Barred at the fifth fret with the root on the low E string, the same chord becomes movable — the shape jazz uses, because the open version cannot be voice-led into the next chord.
Where it shows up
As the I of A major and the IV of E. Both are guitar keys, so the chord appears throughout acoustic and bossa-influenced writing where a plain A would sound too final.
In jazz it closes the ii–V–I in A: Bm7, E7, Amaj7. The open voicing makes that cadence unusually resonant for a jazz progression on this instrument.
It is also the chord that makes bossa nova playable in an open key. Most of the idiom lives in flat keys full of barres; A major seventh, with its ringing open strings, is one of the few places where the style and the instrument agree.