Olivier Messiaen (1908-1992) is regarded by many as the major French composer of the 20th century. An avant-garde composer of great originality, his "extra-musical" interests are broad and varied, as indicated by the title of his collected writings and teaching notes, now being published under the editorship of his widow, Yvonne Loriod Messiaen, the extraordinary pianist and entitled Traite de rythme, ornithologie et couleur. These three large categories, however, do not begin to cover the many other interests he cultivated during his lifetime, including Peruvian folklore, Gregorian chant, and the Tristan legend and its offshoots. My interest in Messiaen's music is of relatively recent origin, inspired to a great extent by the involvement of my wife (Madeleine Forte) not only in the performance of his music but also in writing about it. Particulars of her book on Messiaen and his music are listed on her website. At the present time I am researching the composer's serial music, a relatively restricted body of music written in the short period 1949-1951. This is of special interest because its theoretical basis differs radically from that of the serial music of the composers of the Second Viennese School. Except for the introductory coverage of this music in Robert Sherlaw Johnson's excellent book, Messiaen (University of California Press 1975), I believe there is no published work on this corpus, the central work of which is his Livre d'orgue of 1951, a series of seven remarkable pieces. The music is also of interest historically, since it coincides with the peak of the Darmstadt school, which included several eminent younger (at that time) European composers, notably Karlheinz Stockhausen and Pierre Boulez, both of whom studied with Messiaen.