Popular black-american singing from US. It's made of three verses of 12 bars (the first two of them are repeated) - but also in other schemes - and is based on a tonal scale oscillating between major and minor mode because of the presence of the blue notes or uncertain notes, which are born from the meeting of pentatonic african scale and eptatonic european one. A profane singing suitable for expressing individual feelings (while gospel and spiritual have a religious and collective feeling), blues has its origins in work songs of the slaves and in shouters and hollers of cotton' fields; it spred in the second half of 19th century after slaves' emancipation, in the southern states and in the Mississippi area. It constitutes the first autonomous musical expression of black americans, since it doesn't feel european influence like ragtime, melting with which it has gave birth to jazz. In 1912 William Christopher Handy published Memphis Blues, a song composed thanks to direct inspiration from popular singing. The last examples of original blues, spred about the countries, the "country blues", are recorded by Charley Patton (father of "Delta blues", in Mississippi area), Henry Thomas alias "Ragtime Texas", Huddie Lead Belly alias "Ledbetter", "Blind" Lemon Jefferson. Following the migrations of black people, blues arrived in cities' ghettoes (Atlanta, Memphis, St.Louis, Detroit, Chicago), where it assumes a bigger hardness (Big Bill Broonzy and John Lee Hooker). It has been spred by black minstrels show and in bad night club like brothel and tavern (honky tonky); in these places guitar (used more like a second voice than like an accopmaniment instrument) was substituted by piano. So blues acquired a first instrumental form that gave birth to boogie woogie, a faster blues (Pinetop Smith, Jimmy Yancey, Criple Clarence Lofton); it became a show-genre with singers of Twenties: Ma Rainey (who kept some elements of "country blues"), Mamie Smith (her Crazy Blues, appeared in february 14th 1920, is the first blues record), Bessie Smith (the greatest exponent), Clara Smith, Trixie Smith, Ida Cox, Berta "Chippie" Hill, Sara Martin, Victoria Spivey, etc.. Boogie woogie found its orchestral form during the Thirties in Kansas City (Count Basie), the town which saw the birth of "blues shouters" like Joe Turner and Jimmy Rushing. From boogie woogie take their origins the different ways of rhythm and blues (called in the beginnings "jump"), from which rock was born, as a white version; joining with gospel, blues gave birth to funky, soul music and, at last, disco music.