Blues is a vocal and instrumental form of music based on the use of the blue notes. It emerged 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 influence. The Blues influenced later American and Western popular music, as it became the roots of jazz, rhythm and Blues, and bluegrass. In the 1960s and 1970s, a hybrid form called Blues rock developed from the combining of Blues with various rock and roll forms.   Wikipedia