The 12-bar blues is the longest progression most people know by heart, and the one that rock and roll, R&B and jazz all grew out of. In C it is four bars of C7, two of F7, two of C7, then G7, F7, C7 and a G7 turnaround. Every chord is a dominant seventh, which is what gives the blues its grit: chords that in classical harmony would be tension are, here, the colour of home.
Why it works
The form is three four-bar phrases, and the chords follow the words. The first phrase states a line over I; the second repeats it, starting on IV for contrast and returning to I; the third answers it, starting on V, stepping back to IV and settling on I. That is also a story: home, away, further away, home. The twelve bars are long enough for a verse and short enough to remember, so the progression can carry a three-minute song or a thirty-chorus jam. The dominant sevenths, with their flattened sevenths, match the blue notes a singer bends, which is why the chords and the melody rub together instead of clashing.
The blues’ three chords, C7, F7 and G7, on the keys of C major. C7 is sounding: C, E, G and B♭.
Variants
The quick change
C7 – F7 – C7 – C7 in the first phrase: IV arrives in bar two, the version most rock and roll uses.
The jazz blues
bars 9 and 10 as Dm7 – G7, a ii–V, and a Dm7 – G7 turnaround: The same twelve bars with ii–V–I cadences slipped in.
The minor blues
Minor i and iv with a major V, the sound of slow blues and of a lot of soul.
- The turnaround: the last two bars as C7 – G7, or as C7 – A7 – D7 – G7 in jazz, to set up the next chorus.
- 8-bar and 16-bar blues: the same chords on a shorter or longer frame.
Songs built on it
- Sweet Home Chicago, Robert Johnson (1936)
- Hound Dog, Big Mama Thornton (1952), Elvis Presley (1956)
- Rock Around the Clock, Bill Haley and His Comets (1954)
- Tutti Frutti, Little Richard (1955)
- Johnny B. Goode, Chuck Berry (1958)
- Kansas City, Wilbert Harrison (1959)
- Pride and Joy, Stevie Ray Vaughan (1983)
Related progressions
Piano sounds by the Salamander Grand Piano (Alexander Holm), CC BY 3.0.
