Watch the Min7 Chords online guitar lesson by Matthieu Brandt from Chord Cookbook
The chord formula for a minor seventh chord is 1-b3-5-b7. The chord is minor, meaning it has a flatted third and on the 3 note minor chord we stack a flatted seventh interval on top of the root. The flatted seventh mellows out the minor sound a bit. It creates a more subtle sound that is pleasing to the ear. A minor chord and a minor seventh chord are often mixed up in a progression. Wherever you see a minor chord you can often play a minor seventh.