Captured Tape Technology Launched Postwar Audio Sound in Film

Allied soldiers found the Magnetophon and changed recording forever

When American Signal Corps officer John T. "Jack" Mullin entered a Radio Frankfurt studio in 1945, he found two AEG Magnetophon tape recorders and fifty reels of BASF Type L tape. The discovery was accidental — the Germans hadn't even tried to hide it:

"The reason we didn't know about the Magnetophon was that the Germans never bothered to classify it as top-secret." — Jack Mullin, History of Recording (1972 Billboard interview)

Mullin almost missed the machines entirely:

"On the way back to my unit, we came to the proverbial fork in the road. I could turn right and drive straight back to Paris or turn left to Frankfurt. I chose to turn left. It was the greatest decision of my life." — Jack Mullin, History of Recording (1972 Billboard interview)

When the tape played back, Mullin knew the recording world had changed:

"I really flipped. I couldn't tell whether it was live or playback. There simply was no background noise." — Jack Mullin, Wikipedia, citing Richard James Burgess, The History of Music Production (2014)

Mullin shipped the machines home, rebuilt them, and demonstrated them to Hollywood and broadcast engineers in 1946. The audio community recognized immediately that tape would replace every other recording medium in professional use. (wikipedia)

The 1946 San Francisco demonstration made the case publicly:

"I remember well the first public demonstration I gave in San Francisco to the local chapter of the Institute of Radio Engineers on May 16, 1946. We had a large attendance and the enthusiasm was terrific." — Jack Mullin, History of Recording (1972 Billboard interview)

Bing Crosby's technical producer, Murdo Mackenzie, saw Mullin's demonstration and understood what it meant for broadcast. Crosby hated performing live radio and had been using transcription discs, which degraded audibly. Mullin's tape machines offered broadcast-quality recording that could be edited with a razor blade. The showdown between the existing technology and Mullin's Magnetophons was decisive:

"Then, that awesome moment of playback. Murdo asked first to hear the Ranger machines. My heart sank! The distortion on the peaks was excessive and the background noise was too high. Murdo indicated 'cut' and then asked me to play one of the Magnetophons. We were in!" — Jack Mullin, History of Recording (1972 Billboard interview)

Crosby funded Mullin's continued development, and by 1947 the Bing Crosby Show was the first major American broadcast recorded on tape. Stanford's Henry Lowood described Crosby's role as more than a patron:

"He became very interested in promoting the technology and developing it." — Henry Lowood, Stanford Curator for History of Science & Technology, KQED

Ampex, a small California instrument company, built the first American professional tape recorder — the Model 200 — based on the Magnetophon design, shipping the first units to Crosby in 1948. The ripple effects went far beyond broadcasting — Ampex became one of the seed companies of what would become Silicon Valley:

"So in a way, Ampex was not only the first entertainment technology company in Silicon Valley — it was also close to being the first to generate this culture of employees moving on to found other companies." — Henry Lowood, KQED

(wikipedia)

Tape gave film sound editors their first nondestructive medium

Before tape, film sound was recorded optically — a photographic process that printed the audio waveform directly onto film stock as a variable-density or variable-area track. Editing meant physically cutting the optical negative. There was no overdubbing, no punch-in recording, no nondestructive way to revise a take. If a line reading was wrong, the actor re-recorded the entire passage.

Magnetic tape changed this completely. Sound editors could now splice, rearrange, layer, and remix recordings without degrading the source. Dubbing stages adopted magnetic playback. By the early 1950s, most Hollywood sound departments had transitioned from optical to magnetic recording for production and post-production, even though the final release prints still carried optical soundtracks for compatibility with existing theater projectors.

Magnetic striping on film stock created the first multichannel cinema audio

The same magnetic coating technology that made tape recording possible could also be applied directly to 35mm and 70mm film stock. In 1952, Cinerama premiered with seven discrete channels of magnetic audio striped onto a separate 35mm film running in synchronization with the three-panel image. CinemaScope followed in 1953 with four magnetic tracks striped directly onto the 35mm release print — left, center, right, and surround. This was the beginning of theatrical multichannel sound, and it was only possible because of the captured German tape technology. (wikipedia)

The cost of magnetic striping was significant — it added roughly 10 cents per foot to the print cost, which for a feature-length film meant hundreds of dollars per print at 1950s prices, multiplied across hundreds or thousands of prints. This cost would become the central economic argument against multichannel theatrical sound for the next two decades.