Credit: Getty Images/Ian Dickson/Redferns Jethro Tull ... energised me – you could step outside the comfort zone of twelve-bar blues or pop music and you could do something different.” ...

Nearly a decade later, Bill Haley & His Comets employed the same melody over a 12-bar blues to create “Rock Around the Clock,” the first mainstream rock song.

It's characterized by specific chord progressions, a blues scale, and call-and-response patterns, particularly the twelve-bar blues. The blues has roots in spirituals, work songs, field hollers ...