A major force in contemporary music, Pierre Boulez is committed to the expansion and recreation of musical language. This documentary looks at his work, in particular the creation of Repons, which was heralded as the Signal of "a new age of instrumental achievement" (Financial Times). Boulez is seen rehearsing at his Paris laboratory for new music (IRCAM). He talks about his experimentation, the difficulties involved in communicating his ideas, and the post-war composers who have influenced him.