The journalists had never experienced anything like it, and that wasn’t necessarily a good thing. Packed into buses headed for Yoyogi Park near Sony’s headquarters in Tokyo, Japan, they knew the electronics giant was excited about a product launch set for July 1, 1979. But what had been handed to them after boarding was confusing.

It was a blue-accented device, made mostly of metal and roughly 6 inches long by 3.5 inches wide. Inside was a standard audio cassette. It could be held in one hand, clipped to a belt, or—more awkwardly—hung around the neck. A pair of compact, foam-encased headphones trailed from the unit to the user’s ears, where it emitted a surprisingly rich stereo sound.

But it had no recording feature like Sony’s Pressman, which media members had used for years to document conversations. And the scene at Yoyogi Park was odd: Dozens of Sony staffers were riding tandem bicycles, skateboarding, and swaying while bystanders looked on, baffled. No one was talking; the product announcement was being piped in to reporters via a recording on the device. Sony dubbed it the Walkman, and it insisted it would revolutionize how the world consumed music.

The assembled media members took in the presentation, returned to the bus, and shrugged. Who was going to wear a miniaturized stereo that cost $200 USD?

Enough people, it turns out, for over 400 million Walkmans to be sold in the coming decades; enough for Sony’s profits to grow so substantially that they could afford to buy a movie studio, Columbia Pictures; enough that city officials would declare them a public nuisance that could result in deadly traffic accidents or ear damage.

Sony had anticipated a need and profited handsomely. But while the company became synonymous with the Walkman, there’s a one asterisk to their story—they didn’t actually invent it.

Portable listening devices were, of course, nothing new. Transistor radios grew popular in the 1950s by shrinking components to allow for a pocket-sized listening experience. The drawback was that the user was limited to picking up broadcast stations and whatever playlist the programming director preferred. They were also tinny, the earbuds laughably weak next to proper stereo systems. Real, lost-in-the-music moments were reserved for bedrooms equipped with record players and floorboards that could stand up to the adolescent hysteria incited by Elvis or the Beatles.

Masaru Ibuka’s teenage years were decades in the rear-view mirror, but he identified with their passion for music. A co-founder of Sony, Ibuka was disappointed he couldn’t bring a cassette player with him on long, transatlantic plane rides. Why, he asked engineers, couldn’t they develop a device that was small enough to carry around while allowing the user to listen to whatever he or she wanted?

Akio Morita, Ibuka’s partner, agreed, and the two set a deadline: They wanted a product ready for the start of summer vacation on July 1, a marketing opportunity for people exercising or relaxing outdoors. Under a time crunch, Kozo Ohsone, Shizuo Takashino and other developers took their Pressman—a bulky recorder meant for a niche market—and removed the recording mechanism, adding a lightweight pair of headphones and a stereo amplifier. (To create something completely from scratch would not only take more time, it would be more risk: A prototype that broke down would not go over well.)

Morita took their modified Pressman home and listened to it. It was exactly what he and Ibuka wanted, with one exception: His wife was annoyed at the isolating nature of the device. Morita didn’t want Sony to market a “rude” product, so he had his team add a second headphone jack and an orange button that allowed two listeners to talk to each other through a microphone.

Sony’s Pressman evolved into the TPS-L2, a cassette player designed to resemble antique Japanese lacquered boxes. “Walkman” was taken from both Pressman and Superman, a character recently re-introduced to the public eye because of the 1978 feature film. “Walkman” also hinted at locomotion, the idea of breaking free from home stereos and going where you pleased.

Morita and Ibuka thought they had a hit, but the press disagreed. The lack of a recording feature confounded them, and their apathy leaked into the market. In July 1979, the first month Walkmans were on sale, only 3000 units were sold. In a controlled panic, Sony’s marketing department decided that the Walkman experience was so singular that they would have to be aggressive. Japanese celebrities were recruited for print ads; Sony employees rode trains and patrolled busy pedestrian-packed districts on weekends, extending headphones so consumers could listen for themselves. No ad or slogan could really describe the unique experience of cutting the cord from elaborate home stereos. The Walkman had to be worn to be appreciated.

Sony’s assertive plan worked. Twenty-seven thousand units were sold in August, which depleted the company of its initial 30,000-unit production run. Tourists returned to France, the UK and the U.S. with the devices, seeding the company’s expansion plans. By early 1980, the Walkman was headed for America.

Morita had considered calling it the Soundabout in the States, but “Walkman” was already on the lips of early adopters who had heard of or seen the portable device. Sporting a stylish leather cover, it quickly became an urban accessory must-have. Walkmans in New York became as pervasive as potholes, with users acknowledging one another on the street as though they belonged to the same fraternity.

In their first mention of the Walkman on July 7, 1980, the New York Times declared it a status symbol:

Josh Lansing and the young blonde woman had never even met before, but as they passed each other on Madison Avenue the other afternoon, she waved and smiled and he tipped his headphones in salute ... What the two well-dressed strangers first noticed about each other was that they were both possessors of the newest status symbol around town: the Walkman …”It's just like Mercedes-Benz owners honking when they pass each other on the road,” explained Mr. Lansing, whose cassette hung from his Gucci belt.

Andy Warhol told the Washington Post he preferred the sound of Pavarotti over blaring car horns; beaches that had banned radios took no issue with the solitary nature of portables. The soundtrack of life could not only be changed, but muted.

That latter feature was of concern to Woodbridge, N.J., which passed an ordinance in 1982 that banned the Walkman and its knock-offs from anyone driving or riding a bike on a public street, joining nine other states with similar prohibitions. Wearing headphones for extended periods also concerned audiologists, who feared ear damage from constant musical accompaniment to homework, working out, or isolated jobs like toll collecting or taxi driving. Even repair shops chimed in, saying the parts were too tiny to repair and hanging signs refusing service to the Sony elite.

None of this slowed the Walkman’s momentum. The company shipped over 500,000 units worldwide in 1980 and tripled that in 1981. In 1983, the company introduced the WM-10, which was only a third the size of the original. It featured a “drawer" that retracted when the cassette tray was empty. More importantly, it had earbuds that allowed ambient noise to leak in, easing safety concerns. In 1988 they released the WM-505, the first model with wireless headphones, over 12 years before the first Bluetooth headset.

The Walkman featured prominently in Footloose; Marty McFly used it to terrorize the transistor-era of the 1950s in Back to the Future; “walkmans” became a colloquial term for any portable device in the way Kleenex had become the standard declaration for a tissue.

By the time it entered the Oxford English Dictionary in 1986, Sony had invented, invaded, and conquered an entirely new consumer electronics space.

At least, that's what they had assumed. The same year they made the OED, the company offered a settlement to Andreas Pavel, who for years had taken issue with the “invention” portion of Sony’s story. A devout music lover, he filed a patent in Milan, Italy in 1977 for something he informally referred to as a stereobelt. He tried courting manufacturers, but Philips and Yamaha weren’t interested. Years later, he took note of the Walkman. A case of communal thinking, Pavel was still peeved his discovery had found success without him, though it was for financial rather than personal reasons. "I don't want to be reduced to the label of being the inventor of the Walkman," he told the New York Times.

After two decades of off-and-on court fights, he settled with Sony in 2003. A testament to the Walkman's immense success, the company reportedly cut him a check for eight figures.

Sony

By the late 1980s, the Walkman had grown to accommodate CDs (the Discman) and television (the bulky Watchman). In the 1990s, MP3 devices took up much of their development time, but nothing could anticipate—or compete against—the shift caused by Apple’s iPod in the 2000s. By 2010, Sony announced it would be discontinuing the cassette-based Walkman brand in most territories. Just as Sony users had stamped out transistors and boom boxes in the 1980s to become a societal badge of cool, the iPod’s devotees would settle for nothing less than an Apple.

Cool, of course, is relative. 2014’s Guardians of the Galaxy resurrected both the device and the concept of a mix tape, with Chris Pratt’s Peter Quill using the TPS-L2 as an emotional lifeline to his childhood on Earth. Previously trading for around $100 among collectors, the model shot up to nearly $1000 after the movie was released; a rare “Guys & Dolls” version, which labeled the headphone jacks by gender, can sell for nearly $3000. Thanks to Pratt, the Walkman had come full circle.

Ibuka, incidentally, never quite got his wish. After his team scrambled to modify a Pressman in time for his next international flight, he settled into his seat and hit play. Nothing happened. In their rush to find some classical music for Ibuka to listen to, the engineers accidentally grabbed a bunch of blank cassettes.