A technique to give your twelve bar blues some spice. It is applied as a transition from the 4th bar into the 5th bar (moving the I chord to the IV chord.)
Theory: Chords are played chromatically upwards towards the IV chord from the I chord in a triplet pattern.
Practice: This is most easily described in an example. Suppose we are in the key of C. A 12 bar blues will go as follows:
| C | C | C | C |
| F | F | C | C |
| G | F | C | C |
The part we will focus on is the measure in upper right hand corner (when we are about to change to the IV chord, namely F). Now, instead of playing our usual 4 quarter notes filled with excruciatingly boring old I chords, we "spice" it up with our power change. We play 2 quarter note triplets like so:
C C Db D Eb E
-----o--o--o----o--o--o----
3 3
Legend- o's are quarter notes, 3 means a tri-po-let.
In application, this creates a nice big band effect leading towards the IV chord.
See also: Twelve Bar Blues, Tripolet, Ass | 
