(CNN) It was 40 years ago today that Sony, not Apple, revolutionized the way we listen to music.

The Walkman, a portable cassette player that, for the first time, let us take our music with us without bothering our neighbors, hit the market on July 1, 1979.

The portable cassette player revolutionized how people listen to music.

The Walkman wasn't the first of its kind, but it was the first affordable and manageable portable music player -- others like the German Stereobelt were too clunky and expensive, so they never took off.

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In its heyday, the Walkman was as synonymous with portable music players as Kleenex became to tissue and Xerox was to copy machines.

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