Blues is a genre[2] and musical form that originated in African-American communities in the "Deep South" of the United States around the end of the 19th century. The genre is a fusion of traditional African music and European folk music,[1] spirituals, work songs, field hollers, shouts and chants, and rhymed simple narrative ballads.[3] The blues form, ubiquitous in jazz, rhythm and blues and rock and roll, is characterized by the call-and-response pattern, the blues scale and specific chord progressions, of which the twelve-bar blues is the most common. The blue notes are also an important part of the sound. Blues shuffles or walking bass reinforce the trance-like rhythm and form a repetitive effect called a groove.