Guitar skills: The most common chord progression is known as a ‘12-bar blues’, which, predictably is 12 bars long (eight-, 16- and 24-bar versions are common, too). What the name doesn’t tell you is that you need to know three chords to play the progression.
In E these chords are E, A and B. Simple enough, but, seeing as we can’t guarantee we’ll always want to play in E, we thought we’d better write out the chords in a few other keys too. You’ll notice we’ve labelled the chords I, IV and V.
That’s because the chords always fall on the first (I), fourth (IV) and fifth (V) notes of the key signatures. When you get the hang of the I-IV-V sequence, try applying some of these blues chords to each pitch.