It was a great idea, but it disappeared a few months after it was first introduced.
The flexi disc is, in effect, an audio time capsule preserving the state of speech digitization research in the early 1970s.
A slim square of vinyl, measuring 18 cm on a side, the record is what’s known as a flexi disc, a lightweight alternative to traditional records that became popular after World War II. The technology had many precursors, including German “gramophone postcards” and Soviet “bone music”—jazz or rock recordings pressed on to discarded X-ray film to avoid government censorship. In the United States, the Eva-Tone Company of Deerfield, Illinois became the leading manufacturer of vinyl “sound sheets” (their preferred trademark) by the mid-1960s and promoted their use in “mailing pieces, financial reports, product instruction, sales training, and packaging inserts.”
Due to their low cost, thin form factor, and pliability, flexi discs became the medium of choice for magazine publishers who wished to supplement articles with audio content. Recordings were not limited to musical performances. For example, the December 1969 issue of National Geographic was dedicated to the Apollo 11 lunar landing and contained a sonic retrospective of the Space Race (“Sounds of the Space Age”) narrated by Apollo 8 commander Frank Borman.
You can read more about flexi discs in an article by Benjamin Gross published in the IEEE Spectrum web site at: https://spectrum.ieee.org/history-of-digital-speech.