12 Bar Blues Progression

The term '12 bar blues progression' tells us that there are 12 bars of music, at which point the chord sequence returns to the beginning and repeats itself. 12 bar is very common in blues.

The chords are usually based around the I IV V which is very typical of blues music. In the key of C for instance, the chords will be C F and G. The arrangement of the chords will be something like this. Four bars of C followed by two bars of F, two bars of C, one bar of G, one bar of F, one bar of C and one bar of G. It could be written out like this where each chord name and slash represents one bar.

C / / / F / C / G F C G

Sometimes it is played like this

C F / / F / C / G F C G or C / / / F / C / G / C /

There are other variations but these would probably be the most common. Sometimes a blues is played as an 8 bar or 16 bar. It would be pointless to list every variation. When you listen to a blues song, if you think it isn't a 12 bar then just count the beats to find out how many bars are played before the whole repeats itself.