Twelve bar blues

A basic example of the progression would look like this, using T to indicate the tonic, S for the subdominant, and D for the dominant, and representing one chord per measure:

 T T T T
 S S T T
 D S T T

Many variations are possible. For instance, seventh chords are often used just before a change, and more changes can be added. A more complicated example might look like this, where "7" indicates a seventh chord:

 T  S  T  T7
 S  S7 T  T7
 D  S  T  D7

When the last bar contains the dominant, that bar can be called a turnaround.

Finally, here is an example showing the pattern in the key of D, and how it fits with the lyrics of a given verse. One chord symbol is used per beat, with "-" representing the continuation of the previous chord:

 D        -     -      -        
 Woke up this morning with the 

 G     -   -    -   D - - - D7 - - - 
 blues down in my soul 

 G        -     -      -        
 Woke up this morning with the 

 G7    -   -    -   D - - - D7 - - -
 blues down in my soul            Saying "My

 A     -        -     A7
 baby gone and left me, got a 

 G    -    -     G7 D - - - D - A A7
 heart as black as coal"