A minor major 7th chord is created by adding a natural 7th degree to any minor chord. For example, a Cm (maj7) chord contains the notes C, Eb, G and B (1, b3, 5 and 7). Here are some common open minor major 7th chord shapes.
Dm(maj7)

Ebm(maj7)

Em(maj7)

Fm(maj7)

F#m(maj7)

Gm(maj7)

Bm(maj7)

Cm(maj7)

Dbm(maj7)

Abm(maj7)

Am(maj7)

Bbm(maj7)
