Watch the A Minor 7 Chord Inversions online guitar lesson by Frank Vignola from Inversion Excursion
Now that you have a good grasp on the triads let's move on to adding extensions. We start with adding the minor 7th to the triad to make an A minor 7th chord. Remember: a minor triad is a three note chord consisting of the 1st, flat 3rd and 5th step of the applicable scale. In this case A, C and E A minor triad. Adding an extension to the triad creates a 4 note chord. In this case we are adding the 7th step to the triad. The 7th step of the A minor scale is G. So the spelling of a A minor 7th chord is: A-C-E-G. Let's start inverting. In this case, when playing the G or 7th in the bass this is considered the 3rd inversion. Root position has root in the bass, 1st inversion has the 3rd in the bass, 2nd inversion has the 5th in the bass and the 3rd inversion has the extension or in this case the 7th in the bass. Also remember that an A minor 7th chord has the same notes as the C major 6th chord so you may notice the same chord shapes.
I introduce the famous Doobie Brothers Long Train Runnin' guitar part as the root position A minor 7th chord is what they used. For each inversion, look at the chord and pick out each of the chord tones naming the notes.