Pierre Boulez (born 1925) is a major figure in French musical life, being not only the leading French composer of his generation, but also an outstanding conductor. He is also a prolific writer on music, and this is a translation of his first collection of essays, published in France in 1966. In these essays Boulez worked out many of his most significant ideas about music, and he sets forth his views with characteristic intellectual vigour and acuity. The essays are divided into four parts, the first three concerned with a common preoccupation (aesthetic, technical, polemical), the last a collection of entries intended for a music encyclopaedia. Boulez writes mainly on the giants of twentieth-century music - Stravinsky, Schoenberg, Berg, Webern, Debussy, Messiaen, Ravel - and he offers penetrating and at times provocative analyses of some of their music and musical styles, such as neo-classicism and serialism. His illuminating comments arise from intimate knowledge of the music, and the resulting collection is an essential document of post-war modern music.