With Tonal Allegory, Eric Chafe responds to the serious need for an interpretive study that takes into account the theological content of Bach"s texts and his principles of setting them to music. He sets forth a principle called "tonal allegory" as a fundamental expression of the Baroque concept of music and its relationship to spiritual life. Chafe studies cantatas from all periods of Bach"s life, the two Passions, the Christmas Oratorio, and selected secular works, all with a view towards delineating Bach"s application of the principle of "tonal allegory." One result is the recognition of many patterns of tonal planning and of four basic tonal-plan "types" that appear in many works. For more than three decades Bach scholarship has been dominated by source and editing questions, stimulated by work on the New Bach Edition (Neue Bach-Ausgabe). Here, Chafe hopes to encourage a move toward more interpretive studies, based on a combination of Baroque music theory, historical theology, and the documents of Bach"s time. His work provides a secure basis for an analysis of the development of Bach"s sacred music and thus a beginning for a comprehensive reassessment of one of our greatest musical geniuses.