Eric Clapton, a lifelong student of the blues, has been in more bands that he himself formed than any other guitarist in rock music. He first distinguished himself with the group, the Yardbirds, where he earned the ironic nickname, "Slowhand," for his nimble leads. When the Yardbirds went commercial, Clapton left them to pursue pure blues with John Mayall, a singer, guitarist, and keyboard player who was regarded as the Father of British Blues for his discovery and promotion of luminary musicians in the field. Clapton proved to be Mayall's greatest discovery. On John Mayall's Blues Breakers, Featuring Eric Clapton (1966) Clapton displayed an unprecedented fusion of technical virtuosity and emotional expressiveness, giving rise to graffiti scribbled on walls in London saying, "Clapton is God."

When jazz-trained bassist Jack Bruce joined the Blues Breakers, Clapton grew intrigued by his improvisational style. He recruited Bruce and...