12-Bar Blues

12-Bar Blues is the I–I–I–I–IV–IV–I–I–V–IV–I–I chord loop. In G major that is G, C, and D. The quintessential blues form. Twelve bars of pure soul.

Roman numerals mark each chord's role in the key, not fixed chord names. Uppercase is major, lowercase is minor. 12-Bar Blues uses I–I–I–I–IV–IV–I–I–V–IV–I–I. Change the key and the roles stay; the chord names move with it. In G major you play G, C, D.

Loop G, C, and D. Change on the first beat of each bar and keep the strum steady. If one change is hard, practice that pair slowly, then play the full loop again.

Songs built on 12-Bar Blues include Johnny B. Goode, Sweet Home Chicago, and Hound Dog.

12-Bar Blues (I–I–I–I–IV–IV–I–I–V–IV–I–I) is one of the most reused patterns in Blues and beyond. Writers come back to it because the roles are strong: home, departure, pull, and contrast. It supports almost any melody and still feels complete when you loop it. Same functions, different songs.