Watch the Comping The Blues online guitar lesson by Chris Buono from 40 Day Rhythm SWAT Camp
Jazz players often embellish standard 12-bar, I-IV-V blues progressions with substitute and passing chords, extra Im-V-I cadences, and backcycling progressions. You have to hear these changes before you can start intelligently applying them to your music, and that means learning some jazzed-up blues progressions.
Four-to-the-bar comping is a good place to start. The late Freddie Green, Count Basie's longtime guitarist, was the acknowledged master of this style. He typically used three-note chords voiced on the sixth, fourth, and third strings. These chords sound full and work well for straight rhythm, despite their abbreviated size.
Using a flatpick, play the following C blues progression with crisp, ringing downstrokes. Carefully mute the first, second, and fifth strings. Tape the changes and improvise over them using a C blues scale. You'll find that familiar blues licks suddenly sound fresh and jazzy against more complex changes.
Some quick observations:
In bars 2 and 6, the F#dim7 passing chord moves you smoothly from F (or F7), the IV, back to C (or C6), the I. If you view bar 5's F7 as a temporary I, the preceding Gm7 - C7 change becomes a IIm-V ramp into the F7.
Two more IIm-V-I cadences occur in bars 8 through 11 (Em7-A7-D7 and Dm7-G7-C7). The last three dominant 7ths backcycle in fourths to the tonic: A7-D7-G7-C6. With their strong resolution, the IIm-V-I changes and backcycling dominants provide forward motion, pulling you through the progression and ultimately back to the top.