Blues is a music genre 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 at the end of the 19th century 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. Read more on Last.fm.