Watch the Double-Stops online guitar lesson by Jeff McErlain from Blues Survival Guide: Rhythm Edition
Double Stops are when we sound 2 strings at once, there are triple stops as well, but guitar players still call these double stops. I'm not sure why... Anyway many double stops are derived from the scale related to the key we are in, very often the related minor pentatonic scale. As we can see in this video I am vamping on the A7 chord and my double stops are coming from the A minor pentatonic scale. The bigger picture here is that we can use the related scale to add to the rhythm guitar part. I never understood it when some one would ask me if I played lead or rhythm guitar, to me, it's all the same thing.