The Sonatine for flute and piano (1946) is one of the most performed works by Pierre Boulez and occupies a key position in his oeuvre: as "Opus 1," it reflects his engagement with teachers and role models. This study illuminates Boulez's musical language development through the early version of the Sonatine. Research into his formative years and student compositions weaves a network of connections and addresses fundamental compositional questions: What role did twelve-tone technique play in Boulez's early work? Did he orient himself more towards Anton Webern or rather towards Arnold Schönberg and René Leibowitz? Was the influence of Olivier Messiaen, Igor Stravinsky, and André Jolivet limited solely to rhythm? What other influences seem to emerge? The traces of Boulez's workshop in the Sonatine shed new light on his criticism of his predecessors.