The Flatted Seventh Chords

The 7th chord has a tension that requires resolution. On a tonic, root position, major triad, we learned that the bottom interval was a major third which was made from two whole-steps and the top of the triad was a minor third comprised of a half-step and a whole-step. If we add another minor third (we’ll end up with 4 notes) to the top of this - in other words a half-step and a whole-step - we’ll have a chord that consists of a major third interval followed by a minor third interval and followed by another minor third interval. This is the flatted-seventh chord, commonly referred to as a 7th. So a G7 chord is made using these notes:

G7: G B D F (notice the F is not an F#). The F# is the actual 7th pitch in the G scale, so to form a major G7 chord we would have to use the F# note. Flatting this 7th note “minors” it. This F# is rarely used in bluegrass in a 7th chord, as the more “bluesy” flatted seventh note, F, is preferred.

Often times the tonic chord will add the flatted seventh note creating tension just before a chord change to the subdominant. In the key of G, sound G B D F and notice the tension the F creates wanting to resolve to the color tone of the 4th chord (subdominant). Now form a D7 chord (dominant 7 in the key of G) comprised of the notes D F# A and C. Notice how this C note wants to resolve to the color tone note B in the tonic triad G B D. Switch keys for a moment, and in the Key of C, form a G7 chord and sound these notes and listen to the tension: G B D F. Notice how the F note wants to resolve to the E note which is the color tone of the C chord.

Now play some 7th chords in their inversions starting with root, 1st, 2nd, and 3rd:
G: G B D F, B D F G, D G B F, F G B D
C: C E G Bb, E G Bb C, G C E Bb, Bb C E G
D: D F# A C, F# A C D, A C D F#, C D F# A

Try others.