Let’s begin our exploration of Jazz Blues with a review of the Major 12-bar Blues in its most basic form…
Within each 12-bar chorus, there are three distinct 4-bar phrases…

The deep appreciation of this three-phase structure is absolutely essential for playing 12-bar blues in authentic style.
Phrase #1 presents the main rhythmic/melodic theme and establishes a clear sense of tonic harmony (I)…
Typical Phrase #1:
Phrase #2 is typically a variation of or complement to the main theme. It is played over a temporary IV harmony, with a return back to the tonic I.
Typical Phrase #2:
Phrase #3 typically complements or answers the first two phrases and leads the listener back to the top of the next chorus. It is played over a temporary V harmony with a return to the tonic I.
Typical Phrase #3:
Now let’s combine all three phrases into a 12-bar chorus…

Think of these three phrases as interrelated musical sentences that tell a story. In order to sound/feel “right”, each chorus should be rhythmically and melodically coherent, say something that moves the listener, and lead back to the top of the next chorus or to a logical ending. With some rhythmic comping patterns and tasty licks in your bag and a commitment to this basic formula, your blues playing is guaranteed to blossom!