You can also play through the blues form (which is shown in full in the last example) with a more boogie-woogie feel using Ex. 2 in place of the I chord, E7, and also in place of the IV chord, A7, by shifting the lick up a string to the fourth and fifth strings. Use only downstrokes of the pick, experiment with palm muting to give the notes a powerfull chug. These moves are written out in standard 12/8 shuffle, but they can also be played fast in even eighth-notes à la Chuck Berry.
There’s one slick way to make the riff in Ex. 2 sound much fuller, and that’s simply to add a harmony line on a higher string, as shown in Ex. 3. For the I chord, E7, the harmony line appears on the third string, and for the IV chord, the harmony line resides on the second string. It’s all about memorization—learn the moves (and the fingerings shown) and whether you play this progression fast or slow, on acoustic or electric, you’ll have a rich, evolved way of playing the blues using tasty grips employed by everyone from Michael Bloomfield and Buddy Guy to Billy Gibbons and Eric Clapton. (Extra credit: Add a new turnaround to your blues vocabulary by learning the one shown in the last two bars.)