Help Me, Part 2 - Blues Standards
When a song is hook-driven like this one is, your first approach to accompaniment is to play the hook as well.
The hook on the i7 Chord is 2 2 2 3' 4+ (Root, Root, Root, flat-3rd, 4th). Though he's playing on a Bb Harmonica in 2nd Position, let's reference the C Harmonica in 2nd Position to make talking about the music theory easier. The notes would be G G G Bb C.
If you did your homework over the weekend you would have found that the notes for the iv7 Chord are not available in the low and mid range of the harmonica. The Eb in the C C C Eb G iv7 Chord is only available as a 8'+ (8 blow half step bend), and nobody is going to go up there to play this for accompaniment (grabs too much attention).
The v7 is D D D F G and is easily played as 1 1 1 2" 2 or 4 4 4 5 6+ or 8 8 8 9 9+ (again, we wouldn't play it that high, but it's cool to see that it's available in three octaves).
What do you do about the iv7 Chord?
More on this tomorrow...