6 Magnetic Sound / Pilot Tone

Magnetic sound, the quality of which was decisively improved in 1940 with the introduction of the high-frequency premagnetization process, was increasingly used in film production after World War II.^[25] However, the audiotape was not implemented so much during the showing of a film, but during recording and editing.^[26] Variations in speed when recording sound result in variations in pitch (wow and flutter) and make subsequent synchronization practically impossible. They could be avoided through the use of the respective standardized alternating current frequency (50 or 60 Hz) as power standard for cameras and sound recordings. Methods such as Ranger and Pilot Tone use a similar principle in order to achieve the synchronized speed of the tape recorder and the camera: a pilot-tone generator connected up to the motor of the camera generates a sinus wave that is recorded onto the audiotape as a kind of magnetic perforation. During playback, this tone, even if there were variations in running speed during recording or the audiotape has become deformed, can later be synchronized with the image change frequency. However, one of the advantages of the audiotape, namely the better mobility of the lighter and smaller devices, was restricted by the cable connection to the camera. Yet this restriction could soon be avoided through the standard frequency generated in both devices independent of one another with the aid of an oscillating crystal. On the basis of the relative synchronization achieved in this way, absolute synchrony could then be produced through start and stop signals — such as, for example, a clapperboard or an optical signal controlled by the tape recorder — to be recorded in parallel on both media. The Nagra tape recorder built by Stefan Kudelski asserted itself as the standard audio recorder in film production, at the latest beginning in 1962 with the integration of the Neopilot system, also developed by Kudelski, into the Nagra III.^[27] The emergence of certain film styles that claim immediacy, such as Direct Cinema or cinéma vérité, is frequently associated with the mobility of these audio tape recorders. A film like Nashville by Robert Altman, which is explicitly characterized by an audiotape technique, namely multitrack recording, shows that the audiotape technique is not necessarily bound to a simple documentary quality of its sound. In film, the use of multitrack tape recorders is one of the starting points of a multilayered sound organization that, in comparison to classic Hollywood cinema, is less hierarchical. Hollywood is more oriented toward a central narration and the intelligibility of the dialogue, which is why background noises and music are largely faded out during dialogue. By contrast, Robert Altman’s films, as well as the increasingly important field of sound design in general, often place more emphasis on ambient sound and the overlapping of several sound levels. This allows several simultaneous relations to exist between the soundtrack and the image recorded on film.^[28]