For the learning jazz guitarist, familiarity with the jazz blues progression is essential. It incorporates a number idiomatic changes that are used in many standard jazz tunes, and is a worthwhile addition to your repertoire.
Let's start with the basic framework of the 12-bar progression:
I7 / IV7 / I7 / I7
IV7 / IV7 / I7 / VI7
iim7 / V7 / I7 - VI7 / iim7 - V7
If you're familiar with the 12-bar blues, you'll notice a few differences. It begins with the VI7 in bar 8 (which is F#7 in the key of A). This is followed by a ii-V-I in the key of A, and a I-VI-ii-V turnaround.
Note: If this notation makes no sense to you stay tuned for my introductory "Music Theory for Jazz" articles. You can start with learning about the the diatonic scale.
Anyhow, before we proceed, let's translate the above progression to a chord-progression in the key of A. I'll add a few chord substitutions to color it up a bit.
A7 / D7 / A7 / Em7 - A7
D7 / D#dim / A7 - Ab7 / G7 - Gb7
Bm7 / E7 / A7 - F#7 / Bm7 - E7#5
There are many ways to improvise over this progression, and perhaps the simplest scale to use is A-mixolydian. Consider this your home scale. You can return to this scale if you're not sure what scale to use, or if you lose your place in the tune.
Over the IV chords (D7), you can use D-mixolydian. In fact, you can use the root-mixolydian over any of the dominant chords in the progression. Here's a chromatic descending jazz line in A-mixolydian that you can play over the progression: Descending Jazz Line.
To make it more interesting, you can use the altered dominant scale over any of the 7th chords. With its flattened and sharpened 5ths and 9ths, there is no scale more hip for the Jazz Blues. Here's what the A altered dominant scale looks like:
The formula for this scale is: 1 b2 #2 3 b5 #5 b7
Other interesting scales to try out are: the wholetone scale, lydian dominant, or half-whole diminished.
Enough talk. Below is a short clip of the jazz blues progression, played in the key of A.
I've transcribed the first part of this tune below, which is basically one full progression. The rest of it is left as an exercise to the reader.
Stick around for my follow up articles on jazz blues progressions, where I'll play and transcribe a few lines that work well with it.