Watch the Yee Haa online guitar lesson by Jeff McErlain from Essentials: Advanced Blues Rhythm
What makes this groove sound so big and open is that I'm avoiding playing the third of the chords. I mentioned David Grissom earlier, and this is something I learned from him and Eric Johnson. By essentially playing big power chords, a chord that omits the third, we leave the tonality a little ambiguous. What we get is R-5-R-5.
It also interacts very well with overdrive by removing some of the overtones the third can add, making everything sound very big and sonorous. The ambiguity of the power chord also gives us some very nice leeway when soloing as to how we want to approach the tonality of the song.