Having fun with the 12 bar blues. This music theory lesson explains how the 12 bar blues pattern works and how you can have hours of fun with 12 bar blues. We look at the basic chord scheme, how the 12 bar blues is constructed and then goes on to demonstrate various ways of working with a bass line and with the chords. Even if you,Äôve never played 12 bar blues before you'll soon be making great music.