Watch the The Blues Four online guitar lesson by Tom Wolfe from 50 Hard Bop Blues Licks You MUST Know

Even though the blues progression we've been exploring starts with a dominant chord that has a major 3rd, the 4th can be used as a feature tone and create a nice melodic tension. Using octaves and the flatted-5th to highlight the 4th as a focal point at the beginning of the measure, this tone fits very nicely with the major tonality of the chord.