Musical style Johnson is considered a master of the blues, particularly of the Delta blues style. Keith Richards, of the Rolling Stones, said in 1990, "You want to know how good the blues can get? Well, this is it". But according to Elijah Wald, in his book Escaping the Delta, Johnson in his own time was most respected for his ability to play in a wide range of styles, from raw country slide guitar to jazz and pop licks, and for his ability to pick up guitar parts almost instantly upon hearing a song. His first recorded song, "Kind Hearted Woman Blues", in contrast to the prevailing Delta style of the time, more resembled the style of Chicago or St. Louis, with "a full-fledged, abundantly varied musical arrangement". The song was part of a cycle of spin-offs and response songs that began with Leroy Carr's "Mean Mistreater Mama" (1934). According to Wald, it was "the most musically complex in the cycle" and stood apart from most rural blues as a thoroughly composed lyric, rather than an arbitrary collection of more or less unrelated verses. Unusual for a Delta player of the time, a recording exhibits what Johnson could do entirely outside of a blues style. "They're Red Hot", from his first recording session, shows that he was also comfortable with an "uptown" swing or ragtime sound similar to that of the Harlem Hamfats, but as Wald remarked, "no record company was heading to Mississippi in search of a down-home Ink Spots... [H]e could undoubtedly have come up with a lot more songs in this style if the producers had wanted them." Voice An important aspect of Johnson's singing was his use of microtonality. These subtle inflections of pitch help explain why his singing conveys such powerful emotion. Eric Clapton described Johnson's music as "the most powerful cry that I think you can find in the human voice". In two takes of "Me and the Devil Blues" he shows a high degree of precision in the complex vocal delivery of the last verse: "The range of tone he can pack into a few lines is astonishing." The song's "hip humor and sophistication" is often overlooked. "[G]enerations of blues writers in search of wild Delta primitivism", wrote Wald, have been inclined to overlook or undervalue aspects that show Johnson as a polished professional performer. Johnson is also known for using the guitar