With the growth of the magnetic stripe sound system on other film gauges, the Société commerciale et industrielle Pathé took the opportunity to offer its 9.5mm customers the possibility of adding sound directly to their own films. This innovation brought a fuller amateur-filmmaking experience into the hands of individuals: image, color and sound. Although 9.5mm with sound had existed since 1937 for release prints, amateur filmmakers were restricted to shooting films without synchronized sound and projected their films without any integrated sound system. True to 9.5mm’s reputation as a truly amateur film format, Pathé wanted to design sound recording equipment that would be easy to use at home – and, at a reasonable price. To address this double constraint, the ideal solution was to bring together sound and image directly synchronized on the same medium, as with optical sound. Pathé approached the Pyral company, which had registered a patent for a method of coating magnetic stripes on cinematographic film. A contract was signed between the two companies in June 1951. Pathé was then able to exploit this process exclusively. The company soon after designed a special projector which enabled the application of sound to amateur films, a process referred to as “post synchronous sound. 

The “Marignan” projector was launched in 1952. Based on the “Joinville” model, it was designed to facilitate the recording of magnetic sound on film. Initially available in silent mode, it could be equipped with a magnetic head allowing for both recording and playback. It came with a special amplifier, the JP7, to which a microphone and/or record player could be connected. Besides its main role in generating the pre-magnetization frequency required for magnetic recording, this amplifier also acted as a mixing console for the two sound inputs. Magnetic sound technology had the advantage of being able to capture fully audible information at a speed of 16 fps – the frame rate normally used for shooting 9.5mm films.

At Pathé, the magnetic sound-on-film process was also extended to 16mm film. Simultaneously, the arrival of portable tape recorders allowed synchronous recording of sound and image on separate film and quarter-inch audio tape. However, applying sound after filming and processing was still the most cost-effective, and easiest, method for 9.5mm filmmakers. Following on from the “Marignan” projectors, more sophisticated devices came to market that made it possible to keep using this technique, in this format. The system was still in use as late as 2020.