The present essay is a contribution to film (music) studies, showing the ambivalences postmodernist Hollywood films can produce, moreover a contribution to metalepsis research and intermediality studies. The film under discussion, The Truman Show (u.s.a., 1998), is a highly ambivalent film: it combines traditional Hollywood romance with a non-traditional critique of one of the most important tendencies of commercial (Hollywood) films, namely the creation of such a convincing illusion of reality that the resulting ‘hyper-reality’ (as in ‘reality shows’) begins to blur the boundaries between life and fiction. In The Truman Show, this ambivalence is mainly transmitted by the words and images of the filmic narrative. Yet film music also participates in the ambivalence owing to a remarkable combination of traditional and non-traditional uses. Among the former, the well-known functions of music as emotion-enhancer and bridge between frames play a role. Among the latter category, the (more or less conspicuous) absence of film music in certain scenes is noteworthy, moreover a phenomenon which has not yet found due attention in research: the existence of what in ‘absolute’ instrumental music would be impossible but which the plurimedial combination of music, narrative and the moving image in the sound film can produce, namely musical metalepsis. This is film music that paradoxically transgresses the boundaries of filmic levels both in a top-down and a bottom-up direction. Owing to the lack of attention usually paid to film music in the process of reception (a lack of awareness which, in The Truman Show, is exploited for a thematic purpose), musical metalepsis is not as overt and spectacular as ‘ontological’ metalepses would be in the fields of the verbal and visual channels. Yet it nevertheless enhances a major critical concern of The Truman Show, namely the blurring of ontological levels. In doing so, it participates in the film’s fundamental ambivalence in a particularly noteworthy way: on the one hand, if perceived from a rational and ‘expert’ perspective, musical metalepsis contributes to the implied critique of the delusions of film-based hyper-reality; on the other hand its very covertness illustrates how easily most (‘amateur’) viewers tend to overlook certain filmic devices for the sake of an entertaining emotional immersion in filmic fake-reality and ultimately even hyper-reality.