On: “Talking rubber”, a forgotten audio format

"in 1954 the only way to record sound was to press a phonograph or record sound on film for a movie."

There was wire recording:

https://en.wikipedia.org/wiki/Wire_recording

AMPEX demonstrated magnetic tape recording in 1947, based on the German magnetophone technology used during WWII. Shipments to radio stations began in 1948.

http://www.aes.org/aeshc/docs/company.histories/ampex/leslie...

The Dictabelt also became available in 1947, according to Wikipedia: https://en.wikipedia.org/wiki/Dictabelt

An interesting article about archiving of Dictabelt and other audio format recordings: http://thequietus.com/articles/18004-sound-library-british-l...

Also the Blattnerphone (steel tape):

https://en.wikipedia.org/wiki/Ludwig_Blattner