Watch the Bad Co. online guitar lesson by Robbie Calvo from 50 R&B Licks You MUST Know

The major 3rd double stops sound as good as the 6ths to me, especially if you find out where they work over certain chord progressions.

Taking these ideas up the neck in sequence builds the tension nicely before resolving to the A note out of the A minor pentatonic scale at the 12th fret.