This study is devoted to the very first bars of "Dolphin", a work composed by Elliott Carter in 1980-1981 (the first piece of In Sleep, In Thunder scored for tenor and fourteen intrumentalists). It aims not only at analyzing how the musical text is organized, but also at trying to understand Carter's notion of "composition", i.e. the qualitative transformation of strictly determined structures into musical events. After focusing his attention on pitch- location and musical syntax, the author tries to define the formal function of the prelude and its musical meaning. He finally compares three sketches presenting a rather different aspect of the beginning of the work.