In this essay the author tries a possible analysis and interpretation of the music composed by Nino Rota for "Orchestra Rehearsal", the documentary film made in 1979 by Federico Fellini. The author of this essay, for its proposal of analysis and interpretation of Fellini / Rota masterpiece, refers to the latest analytical methods of film music (especially the ones taken by Sergio Miceli, from which it takes its cue for Perugini your work) considering incidental music, in effect, as a major artistic resources of the twentieth century.