When Radio Was Recorded on Film : The Poste Parisien in 1939

A report published in Benjamin, a weekly magazine aimed at young readers, is proving remarkably valuable today for understanding how a Parisian radio station operated before the war. And the article was written by no ordinary reporter. It was produced by Henri Kubnik, who would later become the creator of Jeu des mille francs (now Jeu des mille euros on France Inter). He takes us inside the Poste Parisien, Paris s most powerful private radio station, owned by the newspaper Le Petit Parisien, which had invested in sophisticated technical equipment to record, correct, cut and edit its programmes much like films.

An Afternoon in 1939

Henri Kubnik walks through the doors of the Poste Parisien building on the Champs-Élysées on an ordinary afternoon in 1939. He looks around. In one studio, around ten actors are bustling around a microphone. They speak, deliver their lines, start again. In another, singers are rehearsing. Further away, an orchestra launches into a series of lively pieces. Everything suggests that a programme is being made. But in fact, it is not being broadcast yet.

At the time Kubnik visits the studios for Benjamin, none of these voices or musical performances is being broadcast. The performers are simply recording programmes . This almost mundane scene, described in the 1939 report, reveals an important transformation in radio: what listeners hear is not necessarily what is happening in the studio at that very moment. A programme may have been recorded several hours earlier. It may even have been recorded days or weeks before it is broadcast. And between the microphone and the radio receiver, there is still a great deal of work to be done.

Choosing Between Disc and Film

The Poste Parisien has a fully equipped recording department, installed in two large rooms in the basement of 116 bis, avenue des Champs-Élysées. In 1935, the station acquired a technical system developed by two Austrian engineers in 1931; Radio Toulouse followed suit. It was the Sélénophone, which the station first used for the broadcast featuring Mireille, which we have already discussed here.

The Poste Parisien therefore has equipment for recording onto discs as well as onto film. The choice of medium depends primarily on when the programme is due to be broadcast.

“When, for example, a programme is recorded in the afternoon and is to be broadcast that same evening, it is recorded onto discs, because a disc can be played back or broadcast immediately after recording. On the other hand, when a programme is not to be broadcast for several days or even several weeks, it is recorded onto film, exactly like a sound film“, writes the reporter.

This detail is crucial. Film is not simply a medium for storing a recording. It makes it possible to do something that is much more difficult with a disc: rework the programme after it has been recorded. But before anything can be cut, we first need to understand how sound is transferred onto film.

The String That Draws Voices

What makes Kubnik s article particularly interesting is the precision with which he explains the technology, clearly with a young audience in mind. The film-recording apparatus consists of two rotating reels enclosed in light-tight housings. The first contains the unexposed film; after passing through the machine, it winds onto the second. The principle is similar to that used for recording sound in cinema.

In front of the microphone, the voice causes a diaphragm to vibrate. This vibration produces variations in the electric current flowing through the wires connected to the microphone. Sound vibrations are thus transformed into electrical variations. Then a tiny but essential component comes into play.

In front of a narrow slit of light is a metal wire that engineers call the string . The string is stretched between the two arms of an electromagnet. At rest, it blocks the slit. No light reaches the film, which therefore records a black line. As soon as someone speaks into the microphone, variations in the electric current passing through the electromagnet cause the string to vibrate. It moves away from the slit, allowing light to pass through. The light then exposes the film.

The voice has become a trace of light. And that trace preserves the characteristics of the sound. The higher the pitch, the faster the string vibrates and the closer together the light traces appear. The more intense the sound, the farther the string moves sideways, exposing a greater portion of the slit: the recorded lines are therefore longer. The result is a genuine soundtrack , similar to that of a cinema film.

Then the Film Gives the Voice Back

To hear what has been recorded, the film must first be developed and fixed. It is then passed through an apparatus similar to those used for projecting sound films. The film is strongly illuminated as it moves past a narrow slit, behind which is a photoelectric cell.

The light traces recorded on the film produce variations in light intensity; the cell converts them into variable electrical currents. These currents are amplified and sent to a loudspeaker. The voice or music is finally reproduced. The journey is remarkable: sound, electricity, light, film, light, electricity, sound. But the most interesting part is still to come. The film can be cut.

Editing to Perfect the Programme

In the studio, the actors work as they normally would. In the control booth are the sound engineer and the sound-effects operator, just as they would be for a live broadcast. But a recorded programme is rarely performed in a single continuous take. It is recorded in sections.

For a historical reconstruction or an evocation made up of several scenes, each scene can be recorded separately. The actors rehearse once or twice. Then, when everything is ready, the producer often referred to as the broadcast director signals to the controller: We re ready ! The recording department is alerted. The machine starts up and, at the same time, the red light comes on in the studio. And off we go.

The scene resembles a film set, right down to the vocabulary. But radio actors have one major advantage: nobody can see them. There is no need for costumes or make-up. Most simply hold their scripts and read their parts. Some programmes are exceptions, notably En Correctionnelle, in which the actors improvise their lines. And above all, a mistake is no longer necessarily a disaster.

Editing a Programme Like a Film

Kubnik emphasizes one of the great advantages of recording onto film: the freedom to make mistakes. An actor mispronounces a few words or stumbles halfway through a sentence? In a live broadcast, the moment is gone as soon as it happens. On disc, correcting it means recording the disc again. On film, the actor simply repeats the sentence.

During editing, the section containing the bad take is cut out and replaced with the correct one. The same applies to a silence that lasts too long. Or to a scene that drags. Editors can cut out a section, rearrange scenes or insert dialogue recorded separately. Kubnik s choice of words is particularly revealing: the programme is edited in much the same way as a film is.

For radio, this is a small revolution. A programme is no longer simply a performance taking place in front of a microphone. It becomes material that can be corrected, reshaped and organized afterwards.

Kilometres of Film to Process

This new freedom comes at a price. The film has to be processed. On the fifth floor of the Champs-Élysées building is a special room containing a large automatic developing tank. It develops, fixes, washes and dries between 700 and 1,000 metres of film an hour. The machine can run throughout the day, processing as much as 8,000 to 10,000 metres of film more than five hours of programmes played back-to-back.

These figures give the report another dimension. Radio recording is not a small-scale operation carried out occasionally by a handful of technicians. The Poste Parisien has a genuine production line. Once developed, the reels pass into the hands of the editors. They cut away unnecessary sections, remove blemishes and splice the pieces back together, one after another, the reporter explains. The first edit is then listened to by the producer, who marks passages that are too long or defective. The editors go back to the film. They cut again, splice it back together, and then the programme has to be listened to once more. And so the process continues.

Kubnik describes a job that can involve cutting and splicing hundreds of pieces of film before the programme is finally deemed ready for broadcast.

The True Cost of Fifteen Minutes

A fifteen-minute programme may require four to five hours of recording. Developing the film takes a little over an hour, corresponding to the time it spends in the machine. But editing takes much longer. Between revisions and repeated listening sessions, the process can take anywhere from eight to twenty hours. After each round of changes, the entire programme has to be listened to again: its duration is checked, its rhythm assessed, and its overall flow considered.

In total, excluding the time required to write the script, fifteen minutes of broadcasting represents an average of fourteen to twenty-five hours of work. Fifteen minutes for the listener. Up to twenty-five hours for the people who make it. That imbalance says more clearly than any explanation what recording changed about radio in 1939.

A Programme No Longer Dependent on Guests Schedules

There is one final consequence, less visible but equally important. Recording makes it possible to separate the moment when an artist performs from the moment when the programme is broadcast. Modern recording techniques therefore make it possible for listeners to hear artists on the radio in the evening while those same artists are performing on stage at the very same time. They can come in and record their contribution in the morning or afternoon, during their free hours.

The voice is no longer bound by the physical presence of the person producing it. This is a significant advance. The actor can be on stage. The technician can be in the control booth. The editor can be working at an editing table. And several hours later, the listener hears their work as a single, seamless programme.

Why the Programmes Were Not Preserved

But this new technology also had a devastating downside for anyone who, today, would like to recover these historical sound archives. As René Faguer, deputy head of the recording department, explained in the magazine Vibrations in 1986 :

Technically speaking, we recorded on Sélénophone, a complicated process, but it was the best available in the field of sound in 1934. The process consisted of recording onto film stock the same kind used for cinema which then had to be developed. It was an extremely flammable material, and I emphasize this point because it explains the destruction of the archives during the war. We stored all our recordings in a kind of bunker on the terrace of the Champs-Élysées building. When space had to be cleared, all the sound films stored there were probably burned.

And so, all that remains today is the loss of a remarkable heritage, gone up in flames.