twelve-bar blues
The most common [chord progression](/term/chord%20progression) in blues music, spanning twelve bars in a I-IV-V pattern
In Depth
The standard twelve-bar blues follows this structure: four bars of I, two bars of IV, two bars of I, one bar of V, one bar of IV, and two bars of I (with a turnaround). In the key of A, this gives A-A-A-A, D-D-A-A, E-D-A-A. Countless variations exist: jazz blues adds ii-V motion, minor blues substitutes minor chords, and bird blues (after Charlie Parker) introduces complex substitutions. The form has been the foundation of blues, rock and roll, R&B, and early jazz since the early 20th century.
An enormous percentage of early rock and roll hits — including Johnny B. Goode, Hound Dog, and Rock Around the Clock — are twelve-bar blues.