A Welsh guitarist, harmonica player, and vocalist, Spencer Davis became one of the elder statesmen of mid-'60s British rock. As part of the Spencer Davis Band, which formed in Birmingham in 1963, Davis scored chart-topping hits on both sides of the Atlantic, including "Keep on Running" and "Somebody Help Me" in the U.K. and a pair of Top Ten singles, "Gimme Good Lovin'" and "I'm a Man," in the United States. The band -- which also featured a teenaged Stevie Winwood on vocals, guitar, and organ, Muff Winwood (Stevie's brother) on bass, and Pete York on drums -- continued to mix...