Whilst jazz may have been born from the blues, it went on to develop its own, separate identity whilst keeping much of the phrasing and deliberate dissonance that characterises the older musical form.
The 12-bar blues is still a hugely common sequence in jazz, but these days the way jazz and blues musicians approach this form is quite different.
Here is a standard 12-bar progression in the key of Bb.
This is the most basic form of the blues but this common variant is also played by many blues players.
Notice the addition of the Eb7 chord in the second bar and the F7 chord in the final bar. Both of these are progressions you will hear played on blues recordings by everyone from Robert Johnson to B.B. King.
By contrast, jazz blues tends to have more harmonic movement created by altering parts of standard blues progressions. As jazz musicians love to reharmonise, there are many 12-bar blues sequences but the following is probably the most common jazz blues progression:
|Cm7||F7||Bb7 / G7 /||Cm7 / F7 /|
Here bars 7-10 have been reharmonised with a I-VI-ii-V progression. This works because the V chord, F7 resolves down a fifth to Bb so the harmonic movement sounds smooth. The same progression is used as a turnaround in the final two bars (each chord is played for 2 beats in these bars).
This progression is one that you can use whenever anyone calls a blues at a jam session as it's considered to be the 'standard' progression for jazz blues.
From here, you can continue to reharmonise the changes in many ways. The most important movement in the blues is the one from the opening chord (Bb7) in the first bar to the chord a fourth higher in the fourth bar (Eb7).
This relationship really defines the blues and these bars are almost never altered. However, you can alter the rest of the progression however you like.
As the chords in a blues are all dominant seventh chords, a common technique is to precede the dominant by its ii chord. For example, the first line could be played as:
|Bb7||Eb7||Bb7||Fm7 / Bb7 /|
Bb7 is the dominant chord from the key of Eb major and has been preceded by the ii chord from that key - Fm7.
The progression can be further reharmonised by preceding the ii chord with a dominant chord a fifth above that. That, in turn can be prededed by it's ii chord until you end up cycling through ii-V progressions until you hit the Eb7 in the fourth bar.
|Bb7||Eb7||Gm7 / C7 /||Fm7 / Bb7 /|
Reharmonising using ii-V progressions was a key device of the be-bop era and Charlie Parker used this technique on a set of reharmonised blues changes that have become so common they're named after him. Sometimes a blues will be called and someone will call out 'Parker changes'. This is what they mean:
|Bb7||Am7 / D7 /||Gm7 / C7 /||Fm7 / Bb7 /|
|Eb7||Ebm7 / Ab7 /||Dm7 / G7 /||C#m7 / F#7 /|
|Cm7||F7||Bb7 / G7 /||Cm7 / F7 /|
Here Parker reharmonises using ii-V progressions in two different ways. In the first four bars, as illustrated earlier, he precedes each dominant chord with a ii chord and each of those is preceded by a dominant chord a fifth above.
In the next four bars, ii-V progressions descend in semitones or half-steps until the final ii-V returns him to the 'home' chord of Bb7.
Because this is supposed to be a 'Quick Tip' (which is already considerably longer than I originally intended!), I won't go into a more detailed analysis here, but if you don't really understand the theory behind the reharmonisations, don't worry too much!
The main thing is to learn the 'standard' jazz blues progression and to be aware that a jazz blues can feature many reharmonisations and be more harmonically dense than the 12-bar progressions commonly played by blues artists.
The most common keys for jazz blues are Bb and F. Eb, Ab, G and C also crop up from time to time. If you're following the advice in my last Power Tip then these are the keys to focus on first.
I'll almost certainly revisit the blues at some point in the future to examine how to approach improvising over jazz blues sequences but in the meantime, I hope you've found this Quick Tip useful.