A minor7th chord is created by adding a flattened 7th degree to any minor chord. For example, a Cm7 chord contains the notes C, Eb, G and Bb (1, b3, 5 and b7). Here are some common open minor 7th chord shapes.
Dm7

Ebm7

Em7

Fm7

F#m7

Gm7

Bm7

Cm7

Dbm7

Abm7

Am7

Bbm7
