Watch the Basic 12 Bar Form online guitar lesson by Andrew Ford from Blues Bass Survival Guide
Let's start with the most common blues song form, the 1-4-5 12 bar blues. The chord structure in the key of C for instance would consist of the 1 chord which is C for 4 bars then we move to the 4 chord, F. Now an easy way to figure out what note matches with each number chord is to take the major scale of the key you are in. As you play the scale give each note of the scale a number starting with the root, C in this case, being #1. The next note D is #2 or the 2nd, E is #3, and F, our next chord in our blues progression is #4 or the 4 chord in the key of C. With this knowledge you can figure out chord numbers in whatever key you are in. So we will play that 4 chord, F, for 2 bars. Next we will return to the 1 chord, C, for 2 more bars which makes 8 total bars so far. Now for the last 4 bars we will introduce a new chord, the 5(V) chord, which will be G and play it for 1 bar. Then we will return to the 4(IV), F, for 1 bar and finish by going back to the 1 chord, C, for our last 2 bars. This is our most basic 12 bar blues form. We will take a look at some of the many variations of this form later in the course.