Pierre Boulez spent a great deal of time in post-war Germany. His close connection with the country began when Heinrich Strobel commissioned him to compose Polyphonie X, initiating his ongoing close contact with both Strobel and the city of Baden-Baden, where he would take up residence in 1958. The chapter considers the 1951 premiere of Polyphonie X at Donaueschingen and the controversy which followed. It also contextualises the piece within the various compositional projects Boulez was preoccupied with at the time. The chapter considers Boulez’s attitude towards dodecaphony as focused on the Second International Twelve-Tone Congress of 1951 and his reflections on how Webern might be approached profitably by composers of new music. Given Boulez’s move to Germany in the late 1950s, the chapter reviews his disillusionment with the musical scene in France and the fact that a number of his most important compositions were first premiered in Germany.