D Minor 6th
m6
0 - 3 - 7 - 9Minor + major 6th
About D Minor 6th
D minor sixth places a B natural over a D minor triad — D, F, A, B — and the chord sits awkwardly between two worlds: the notes belong to G major, the root belongs to D minor, and which one the ear believes depends entirely on what comes next.
The notes
D, F, A, B. The B is the major sixth, and it is the note that keeps this chord out of the key of D minor proper — that key uses B♭.
Read from B the same notes give B half-diminished; over a G bass they give G9. The chord therefore functions as a dominant far more often than as a minor tonic.
On the fretboard
The open shape modifies D minor by adding the B on the G string at the fourth fret, or by leaving the B string open in a partial voicing. The second is easier and thinner.
At the fifth fret with the root on the A string the chord becomes movable, and that is the form used when it functions as a rootless dominant.
The awkwardness of the open shape is instructive. Every finger has to avoid the open E string, which does not belong to the chord — a reminder that the guitar helps only when its open notes happen to agree with the harmony.
Where it shows up
In swing and gypsy jazz as a tonic in D minor, and in comping as a substitute for G9. It also appears in minor blues, where it replaces Dm7 on the home chord.
Its use in modern popular music is rare, and that rarity is itself informative: the minor sixth belongs to a harmonic vocabulary that predates rock and never fully returned.