This is one of the early styles of blues where rock and roll music started. From the word itself says it is composed of twelve bars. It has three chords which are named I, IV, V. The diagram below is in the key of G. Therefore I is equivalent to G, IV as C, and V as D. Examine the illustrations below:
Play chords 4 counts before moving to the next bar.
Here's another version:
The only difference from the first illustration is that C and D7 chords were used on the 10th and 12th bar respectively.
Another way of playing twelve-bar blues is through shuffle.
