Music's relationship with emotion has been the subject of numerous philosophical and psychophysiological studies in recent years. The question of whether music merely expresses or actively arouses emotion in its listeners, however, gains added complexities when considered in the context of film. What is going on, for example, when we believe ourselves to be afraid in the cinema; and how does the presence of a musical heartbeat contribute to this feeling?
In this article I answer those questions, firstly by invoking the notion of 'perceptual realism' and questioning a number of comfortable givens in film music theory (including the nondiegetic status of music), and secondly by proposing a 'heartbeat hypothesis' that combines empirical and philosophical approaches to musical emotion with theories of cinematic fiction. This hypothesis suggests that heartbeats are effective at helping us experience 'fictional fear' precisely because the real-world emotion of fear is fundamentally about the body; that there is a strong relationship between our response to music and our own ability to produce sounds (Cox's 'mimetic hypothesis'); and that, as a result, we may recognise and interpret certain cinematic musical gestures in the context of our own corporeality as fear-inducing. I explore a number of film scenes that feature the sound of heartbeats, or heartbeat rhythms in their scores, before making some comments on the wider implications of the hypothesis for film music theory in particular, and musicology in general.