Watch the Double Stops online guitar lesson by Brad Carlton from Guitar Lab: Big Blues & Beyond
This lesson covers double-stop licks in which the b7 is the upper voice. The sound produced with this technique will remind you of B3 organ style playing.
We'll begin with the b7 of the C blues scale 6th string root form in the eleventh fret of the 2nd string. This will be the upper voice. Then you'll play the C blues scale that exists below it on strings 3 through 6.