"There are a number of different ideas as to what the blues really are: a scale structure, a note out of tune or out of key, a chord structure; a philosophy?

The blues is a form of Afro-American origin in which a modal melody has been harmonized with Western tonal chords. The 'blue notes' or blue tonalities are one of the defining characteristics of the blues. [...]

Blues lyrics contain some of the most fantastically penetrating autobiographical and revealing statements in the Western musical tradition. For instance, the complexity of ideas implicit in Robert Johnson's 'Come In My Kitchen,' such as a barely concealed desire, loneliness, and tenderness[...]

Blues lyrics are often intensely personal, frequently contain sexual references and often deal with the pain of betrayal, desertion, and unrequited love or with unhappy situations such as being jobless, hungry, broke, away from home, lonely, or downhearted because of an unfaithful lover.

Some feel that the blues is a way to approach music, a philosophy, in a manner of speaking. Whatever one may think of the blues, it was their "strong autobiographical nature, their intense personal passion, chaos and loneliness, executed so vibrantly that it captured the imagination of modern musicians" and the general public as well. "

This text is an extract of Robert M. Baker "Where do the Blues come from? or A Brief History of the Blues" http://www.island.net/~blues/faq1.html