 Although the first impact of the British Invasion on American popular music was through beat and R&B based acts, the impetus was soon taken up by a second wave of bands that drew their inspiration more directly from American blues, including the Rolling Stones and the Yardbirds.British blues musicians of the late 1950s and early 1960s had been inspired by the acoustic playing of figures such as Lead Belly, who was a major influence on the Skiffle craze, and Robert Johnson.Increasingly they adopted a loud amplified sound, often centered on the electric guitar, based on the Chicago blues, particularly after the tour of Britain by Muddy Waters in 1958, which prompted Cyril Davies and guitarist Alexis Korner to form the band Blues Incorporated.