Blues is a language--one which has evolved its own rules and which is the sole property of a culture always forced to the periphery of white society. As such it is a political language. Whether it is passed as a legacy from African village to Mississippi farm, or from farm to Chicago ghetto, or from ghetto to Paris cafe, it is part of a larger oral heritage that is an expression of black America. Makeshift instruments, runaway slaves, railroads, prisons,...