Blues is a musical genre and form that originated in the deep south of the United States in the 1860's. The blues included ghosts, work songs, screams, chants and simple narrative ballads, rhymes of African American culture.
The blues form is ubiquitous in jazz, rhythm and blues, and rock and roll and is characterized by a call-and-response pattern, a bluesy scale, and specific chord progressions, with the twelve-bar blues being the most common. Notes (or "worry notes"), usually thirds, fifths, or flatted sevenths in the key, are also an integral part of the sound. Mixtures of blues or walking bass amplify the rhythm of the trance and create a repetitive effect called the groove.
