Knowing your twelve bar blues chord progressions is one of the best ways to get a handle on playing guitar. Once you understand the basic principles of blues guitar, you can start to experiment with improvising within the chord progressions and to put your own mark on the music.

The twelve bar blues chord progression is very widely used in pop and rock music. If you have listened to and tried to play some blues songs, you will understand how popular this basic chord sequence is. In playing blues guitar you take the main chord of the song you are playing, which is called the "tonic", the fifth step of the scale - the "dominant", and the chord below the dominant, the "subdominant", or fourth step. So if you are playing a song in the key of E your tonic chord is E, the subdominant is A and the dominant is B. If you are playing in the key of A, your chords are A, D and E.

In musical notation your chord sequence is commonly written in Roman numerals. In the case of the twelve bar blues chord progression, it will be written as I IV V. Using this notation you can tell which chords you will be using in any key.

So let's look at how the twelve bar blues chord progression actually progresses. Well, the first four bars use the tonic chord, in the fifth and sixth you play the subdominant, in the seventh and eight you will play the tonic again, in bar nine it's the dominant, in bar ten it's the subdominant and in the eleventh and twelfth bars it's the tonic, or in this bar the dominant seventh chord is usually used to prepare for the tonic chord to begin the progression again.

The fact is that the seventh chord is used a lot in blues music rather than just the straight major chord. This will make the chord sequence in the key of E look like this:

E7 E7 E7 E7

A7 A7 E7 E7

B7 A7 E7 E7

Or you could just play the seventh chords in the fourth and twelfth bars like this:

E E E E7

A A E E

B A E E7

Or you could play all major chords except for the subdominant and the final bar:

E E E E

A7 A7 E E

B A7 E E7

So there you have a couple of variations in the twelve bar blues chord progression already. Once you have the feel of the progression using open chords, you can try experimenting with the barre chord and power chord versions of the basic chords.