Watch the Playing a 12 Bar Blues online guitar lesson by TrueFire from Beginner Guitar Explorations
Lesson Source: Susan Mazer's Hands-On Guitar: The Beginner's Guide
Now we're going to apply these chords to what’s called a 12-bar blues. This means that there are 12 measures (sometimes called a bar) in our form. We'll keep repeating the same 12 measures over and over. You'll see that this form is used outside of the blues often in all styles of music.