In this groundbreaking book, acclaimed film music author Kevin Donnelly offers the first sustained theorization of synchronization in sound film. Donnelly addresses the manner in which the lock of the audio and the visual exerts a perceptible synergy, an aesthetic he dubs occult: a secret and esoteric effect that can dissipate in the face of an awareness of its existence. Drawing upon theories of sound from Sergei Eisenstein to Pierre Schaeffer to Michel Chion, the book investigates points of synchronization as something like repose, providing moments of comfort in a potentially threatening environment that can be fraught with sound and image stimuli. Correspondingly, lack of synchrony between sound and images is characterized as potentially disturbing for the viewer, a discomfort that signals moments of danger. From this perspective, the interplay between the two becomes the central dynamic of audio-visual culture more generally, which, as Donnelly argues, provides a starting point for a new understanding of audio/visual interactions. This fresh approach to the topic is discussed in theoretical and historical terms as well as elaborated through analysis of and reference to a broad selection of films and their soundtracks including, among others, Singin' in the Rain, Saw, Shanghai Express, and Assault on Precinct 13.