Blues is a vocal and instrumental form of music based on the use of the blues chord progressions and the blue notes. Though several blues forms exist, the 12-bar blues chord progressions are the most frequently encountered. Blue notes are sung or played at a slightly lower pitch than that of the major scale for expressive purposes. Blues emerged as an accessible form of self-expression in African-American communities of the United States from spirituals, work songs, field hollers, shouts and chants, and rhymed simple narrative ballads. The use of blue notes and the prominence of call-and-response patterns in the music and lyrics are indicative of African influences. The blues influenced later American and Western popular music, as it became the roots of jazz, rhythm and blues, bluegrass and rock and roll. In the 1960s and 1970s, blues was popularized in a hybrid form called blues rock.
The term "the blues" refers to the "the blue devils", meaning melancholy and sadness; an early use of the term in this sense is found in George Colman's one-act farce Blue Devils (1798). Though the use of the phrase in African American music may be older, it has been attested to since 1912, when Hart Wand's "Dallas Blues" became the first copyrighted Blues composition.In lyrics the phrase is often used to describe a depressed mood.
Robert Leroy Johnson (May 8, 1911 – August 16, 1938) was an American blues musician, among the most famous of Delta blues musicians. His landmark recordings from 1936–1937 display a remarkable combination of singing, guitar skills, and songwriting talent that have influenced generations of musicians. Johnson's shadowy, poorly documented life and death at age 27 have given rise to much legend.
Considered by some to be the "Grandfather of Rock 'n' Roll", his vocal phrasing, original songs, and guitar style have influenced a broad range of musicians, including Muddy Waters, Bob Dylan, Jimi Hendrix, Led Zeppelin, The Rolling Stones, Johnny Winter, Jeff Beck, Jack White and Eric Clapton, who called Johnson "the most important blues singer that ever lived". He was also ranked fifth in Rolling Stone's list of 100 Greatest Guitarists of All Time.