an African-American folk music idiom, a forerunner of jazz and a major influence on 20th century American popular music. .
a song-form with an AAB rhyming scheme in three four-bar segments--each one part vocal, part instrumental response--using a I-IV-V chord progression, including chords with flatted "blue" notes, usually thirds and sevenths. .
a musical state of mind. .
All true, none of them true enough.
The origins of the blues precede recorded music, and even after the arrival of the phonograph, the blues was regarded as such a low-class and/or simply un-commercial form that it existed for a full 20 years before it was recorded. In the wake of the Civil War, blacks' field hollers and work songs, cross-blending the various music traditions brought by the slaves from Africa, began being developed into songs. Anglo-Saxon church music and folk-ballads were also transformed into forerunners of blues and gospel songs, again drastically influenced by the ex-slaves' African musical heritage. Another strain entered the mix with the jumped-up dances and songs popular in medicine shows. Initially, the blues instruments of favor were the harmonica--cheap, easily portable, and, in the African manner, an instrument capable of imitating the human voice--and the banjo. .
The form began coalescing just around the turn of the century, with the more familiar guitar and piano gaining currency. Musicologists' best guesstimates place the blues as chiefly arising in three regions: Texas, Georgia/the Carolinas, and, most notably, Mississippi (especially the Delta area), possibly as soon as the 1890s but definitely by the early 1900s. The blues piano, however, developed in a parallel but different course--the players could only go where the pianos were, namely whorehouses and barrelhouses. Blues piano fermented principally in the eastern Texas/western Louisiana area, but soon spread, especially to the cities in the Midwest.