The 12 bar blues are defined by a repeating pattern of chords. Each cell in the table below is a measure--12 in all.
| I | I (IV)* | I | I | IV | IV |
| I | I | V | IV | I** | V** |
*you can also use the IV chord for a “quick change” progression to add variety
**these two measures are the turnaround measures, and you often do some “walking” between the chords here, or play a standard blues turnaround
