Blues is the name given to both a musical form and a music genre created primarily within the African-American communities in the Deep South of the United States at the end of the 19th century from spirituals, work songs, field hollers, shouts and chants, and rhymed simple narrative ballads. The blues form ubiquitous in jazz, rhythm and blues, and rock and roll is characterized by specific chord progressions—the twelve-bar blues chord progressions being the most common—and the blue note, notes that for expressive purposes are sung or played flattened or gradually bent (minor 3rd to major 3rd) in relation to the pitch of the major scale.