Blues is a genre of Afro-American folk and popular song. It is generally 12 bars long, falling into three phrases of four bars each (one phrase for each line of text). The most typical chord pattern for these phrases is based on the first, fourth, and fifth notes of the scale: phrase 1-III; phrase 2-IV II; phrase 3-VV (or V) II. Each phrase of sung text is normally followed by instrumental improvisation, creating a call-and-response pattern. Blues music uses a scale in which the third, fifth, and seventh notes are freely "bent" or microtonally flattened in comparison with the standard major scale. Blues tends to deal with the hardships of life and the sadness of love. Blues singing, rooted in various forms of black American slave song, was widespread in the southern U.S. by the late 19th century. "Archaic" and "country" blues differed widely in their lyric and musical form; singers typically accompanied themselves on guitar or harmonica. Later singers in this style include Blind Lemon Jefferson and Leadbelly. In 1912, with the publication of "Memphis Blues" by W.C. Handy, blues entered the range of popular song. Classic "city" blues evolved in the 1920s and 1930s in the singing of Ma Rainey, Bessie Smith, the others. Lyric and musical forms became largely standardized, and singers often worked with jazz band or piano. Adapted to solo piano, blues gave rise to boogie-woogie piano playing. Blues and jazz overlapped, sometimes almost indistinguishably, and blues was considered a nurturing form for early jazz, but blues also developed independently. In the 1940s singers such as T-Bone Walker and Louis Jordan performed with big bands or with ensembles based on electric guitar, acoustic string bass, drums, and saxophones; the electric organ also came into use about this time. After 1950 B.B. King, Ray Charles, and others used improved electric guitars and louder, electric basses; brass instruments often replaced saxophones.