B Major 6th
6
0 - 4 - 7 - 9Major + major 6th
About B Major 6th
B6 adds a G♯ to a B major triad, and on guitar it is a barre chord at the second or seventh fret with no open strings to soften it. The sixth removes the finality of the major triad, which is useful in a key where the tonic is already hard enough to reach.
The notes
B, D♯, F♯, G♯. The G♯ is the major sixth, and the same four notes read from G♯ give G♯ minor seventh — the relative-minor equivalence common to every sixth chord.
Because none of the notes is available open, the chord sounds uniform wherever it is played, which is an advantage in arrangements that move it around the neck.
On the fretboard
Second fret with the root on the A string, or seventh with the root on the low E. The seventh-fret position is easier and is where most players put it.
The compact four-string voicing is standard in swing, where the chord is struck and muted rather than allowed to ring.
Where it shows up
As a tonic in B major at the end of phrases, chiefly in jazz and swing arrangements. It also appears in blues in E as the V chord with added colour.
On guitar the key arrives by transposition more often than by choice, so this chord tends to come from a chart rather than from the instrument.
The chord is also common in Hawaiian and lap-steel playing, where whole tunings are built around sixth chords and B is a natural position for the instrument. Standard-tuned guitarists inherit the sound without inheriting the ease.