Sony TC-50

It was conceived for the purpose of dictation but gained popularity with the general public after its use during the Apollo program lunar missions.

[1] Procured to facilitate the recording of personal mission logs, negating the need for additional paper work, the TC-50 was also used by astronauts to play their favorite mixtapes in the Apollo spacecraft.

"Rather than blast off with only blank cassettes, the astronauts took tapes that had been pre-filled with music befitting their tastes" and recorded over them as the mission advanced forward.

[2] Neil Armstrong, Buzz Aldrin, and several other astronauts were provided with cassette recordings by Al Bishop and Hollywood producer Mickey Kapp.

[1] The TC-50 has variously been described as a "predecessor" or "proto-Walkman" due to its compact design and similarity.