GREENE'S BIOGRAPHICAL ENCYCLOPEDIA OF COMPOSERS by David Mason Greene (Doubleday: $30). There exists in classical music lexicology a sort of gray area. Bounded on one side by the Great Wall monolith of Grove's Musical Dictionary and the Slonimsky-barbed Baker's Biographical Dictionary of Musicians and on the other by the finger-popping gushes purported to "outline the history of music" in 100 pages, this gray area includes many works of considerable utility; Harold Schonberg's several books on the great figures in music could be placed in this category. Among these, we can include the present offering, which, while witty, informed and actually quite helpful, is crippled by an inexplicable indexing system which arranges the 2,400-plus composers and musikants by birth date rather than by their names. In a preface, David Greene defends his Byzantine system by noting that it "places composers in a historical perspective" and allows the book to be read "as a sort of history of music in Western civilization." Were he to have limited himself to 500 or so of the more prominent figures in music, this might have been the case; but when one finishes Mozart's entry, for example, one reads on about Johann Christoph Vogel, "the scion of a family of violin makers," and any sense of artistic perspective is lost. Only by constantly flipping backward to the alphabetical concordance and then forward again can you find your way through the thicket of Vogels. A shame, for much of what Greene has to say is pointed and graceful. Greene throughout enlightens by making the mass (or lack) of information accessible to any interested music lover, not just the musicologist or working musician.