"'The songs of a slave are word-pictures of every thing he sees, or hears, or feels.'--John Dixon Long, a Philadelphia clergyman, 1857. The cacophony of clanking chains intruded upon the euphony of human song during the "Middle Passage" when--at the behest of ships' officers--slaves being transported to the Americas caused the overcrowded ships to echo with the sounds of dancing feet and harmonious voices. That scene is one of the first which Dena...