In his book, Discovering Robert Johnson (which he co-authored with several other writers), Clapton said of Johnson, that he was "..the most important blues musician who ever lived. He was true, absolutely, to his own vision, and as deep as I have gotten into the music over the last 30 years, I have never found anything more deeply soulful than Robert Johnson. His music remains the most powerful cry that I think you can find in the human voice..."
Clapton was influenced by the blues from an early age and practiced long hours to learn chords of blues music he listened to, playing along to the records. He preserved his practice sessions using a portable reel-to-reel tape recorder.
Around this time Clapton began busking around Kingston, Richmond and the West End of London. In 1962, Clapton started performing as a duo with fellow blues enthusiast David Brock in the pubs around Surrey. When he was 17 years old Clapton joined his first band, an early British R&B group, The Roosters, and played briefly with Casey Jones & The Engineers.
The close friendship between Clapton and Harrison resulted in Clapton's playing on Harrison's "While My Guitar Gently Weeps" from the Beatles' White Album. That same year, Harrison released his solo debut Wonderwall Music, becoming the first of many Harrison solo records to feature Clapton on guitar.
Other media appearances include the Toots & the Maytals album True Love where he played guitar on the track "Pressure Drop." He can also be heard at the beginning of Frank Zappa's album, We're Only in It for the Money.
Clapton frequently appears as a guest on the albums of other musicians. For example, he is credited on Dire Straits’ Brothers in Arms album, since he lent Mark Knopfler one of his guitars for the album. He also played lead guitar and synthesiser on The Pros and Cons of Hitch Hiking, Roger Waters' debut solo album.