The paper analyses the instrumental exposition of Ivo Malec's Lumina, until the entrance of the magnetic sound track, in order to enlighten how the composer builds up and structurates the sound material of this mixed work from the possibilities of a string orchestra. The instrumental exposition is articulated on two fundamental, initial and terminal trames, which together occupy a large time span: about 2'30 for 3'49 of total duration of the exposition. The paper first describes the material of these two trames, then analyses their treatment trough dynamics, mutations and imbrications, and the evocation of studio techniques. The relation to traditional values of pitch and duration is elucidated. The string orchestra creates a rich morphologic universe of which the values of pitch and duration are constituents at the same level as many other sound criteria, from which the musical expression gains much force. The exposition, as in a sonata, brightly presents the work in its fundamental implications.