12-Bar Blues (I⁷–IV⁷–V⁷)

The 12-Bar Blues progression: I⁷–IV⁷–V⁷ — in the example key of A, that is A7 – D7 – E7.

The backbone of blues, rock and roll, and country: three dominant-seventh chords stretched across a repeating 12-measure form. Once you know the pattern you can jam along with thousands of songs without ever seeing a chart. In the example key of A the chords are A7 – D7 – E7. Songs built on it include Johnny B. Goode; Sweet Home Chicago; Hound Dog. Its mood palette leans bluesy & jazzy.