Sony had released Japan's first tape recorder, the G-Type, and its Soni-Tape branded magnetic tape back in 1950. The machine had been adopted in government offices, schools, broadcasting stations, and finally into the home. They used completely exposed tape reels and were quite difficult to operate, however, and going into the 1960s, the need for small and easy-to-use cassettes was growing.

Sony had actually sold a smaller tape recorder using two overlapping tape reels inside its case all the way back in 1957, called the "Babycorder." The product failed to catch on, and facing the need to develop an international standard for the simple and convenient cassette, Sony changed lanes and began talks with other companies around the world on standardizing the cassette tape.

It was during this period that German electronics company Grundig and Dutch electronics company Philips would each seek to set their own cassette formats as the industry standard. Grundig had developed the DC-International format alongside two other German manufacturers, while Philips had produced the Compact Cassette. Ohga, then head of Sony's second production department, would choose the slightly smaller Philips Compact Cassette.

When drawing up the contract between the two companies, royalties inevitably became an issue. Unwilling to accept Philips' royalty prices, Ohga forcefully demanded that "if you ask us for a single cent in royalties, we'll be working with Grundig." Philips folded, and the cassette license was granted to Sony for free.
Taking antitrust laws and their own trustworthiness as a business into account, however, Philips could not make licensing free for only Sony - as such, Philips would make the move to offer its Compact Cassette license to all manufacturers free of charge, on the condition that manufacturers would maintain strict compatibility between their products.

Sony's first cassette tape recorder to use the Compact Cassette would be the TC-100, released in 1966. Cassette use would continue to expand from there, resulting in the production of integrated radio-cassette boomboxes as cassettes quickly became a universal aspect of life in the home and in car stereos across the globe.

Yet at that time, lightweight tape recorders that could be carried around while walking were limited to models with monaural speakers built into the recorder body. Sony attempted to address this gap in 1978 with the diminutive TC-D5 model, capable of both recording and playing stereo sound. Weighing around 1.7 kilograms (3.74 pounds) and being the size of a textbook, however, the product was far from being considered "lightweight." Ibuka, himself a music lover, took the TC-D5 and a pair of headphones with him on a business trip abroad, and although he enjoyed listening to music in stereo sound on the plane, he also deemed the product to be too heavy.

One day, preparing for another business trip to the United States, Ibuka approached Ohga and made a request: "I can do without recording, so could you just install the circuits for stereo sound into this Pressman?" The Sony Pressman was a tape recorder with an inbuilt monaural speaker, sold in 1978 and small enough to fit into the palm of one's hand. Ohga brought Ibuka's request to the head of Sony's tape recorder department, Kozo Ohsone, who directed his department's engineers to remove the recording function from the Pressman and install stereo sound capabilities in its place. Attaching some headphones they had on hand to the new device, the engineers gave it a listen and found the audio quality to be unexpectedly good, when Ibuka suddenly appeared through the door. Taking the headphones into his own hands and giving it a listen, he happily exclaimed, "Despite its size, the sound's quite good, isn't it? You really do need good headphones that can pick up all the sounds without missing anything when you're listening to real music."

Returning from his business trip overseas alongside his modified Pressman, Ibuka had quickly taken a liking to his modified machine and immediately showed it to Morita. "Give it a listen. What do you think? A stereo cassette player you can listen to while walking," he excitedly told Morita. Morita too found the device quite charming. "It's really quite different to listening with speakers. Plus, you can carry it around and listen to tapes all on your own. This might be big," he reflected. Morita's keen business sense was tingling.

"It is imperative that, when we test a product concept by bringing our first model to market, it has as few malfunctions as humanly possible. If the device is viewed as fragile or dysfunctional, then the concept also ends up in the trash."
Ohsone had learned this lesson from experience, and the team was especially pressed for time this time around. Under Morita's advice, the internal mechanisms for the product's first model would be repurposed from the Pressman, which was an already established product with five hundred thousand units sold.

There were surprisingly very few technical issues with the product's first model. The technology backing the concept was already well established, so Shizuo Takashino and his engineering team devoted all their efforts to making the machine as failsafe and reliable as possible.

On the other hand, given the product's completely novel nature, worries were rampant about whether the product would be received positively, as well as about how to even market the new idea. Starting with the product's naming, a young employee in the marketing department decided to name the new product the "Walkman," inspired by the names of the original Pressman and the popular superhero character Superman. The name fit perfectly with the device's ability to let users take it out of the house and listen to music while walking or moving around.
Although others in the company thought the name wouldn't make grammatical sense in English, Morita backed the original idea's creator. "This is something for the younger generations. If they say it's good, then that's that," he said. It was decided: the new device would be named the Walkman.

There were still many people in the company who had their doubts about the Walkman, however. "No one wants a `tape player` that can only play tapes. If it can't record anything, it'll never sell," some objected. Still, Morita trusted his instinct. Under his direction, the Walkman would launch with a first batch of thirty thousand units - a lofty amount given that fifteen thousand units sold per month was considered on the higher end for tape recorders at the time. Preparations continued despite the uncertainty, and at last it was time to announce the Walkman on June 22.

To get the word out on this new portable style of music listening, Sony chose some quite creative tactics when announcing the product to the press. First inviting reporters to the Sony Building in Ginza, the reporters were then all asked to board a bus, where they were handed the new Walkman then and there. Taking the bus to Yoyogi Park, the reporters were then instructed to hit the play switch on the product they had just received, whereupon music and an explanation of the Walkman immediately came flowing through their headphones. As they listened, workers from the marketing division and college students hired for the event, all dressed in Walkman T-shirts, would demonstrate the new mobility enabled by the Walkman by jogging and moving around the park.

The media response was, however, mild at best. Most newspapers didn't even report on the new product, and those that did only wrote a few sentences in summary. Although the Walkman went on sale on July 1 without a hitch, only three thousand units had sold by the end of the month.

At first, people didn't understand the idea of walking around town with headphones on. To introduce this brand-new style of music listening to the public, members of the advertising team and the domestic sales team had each taken a Walkman with them onto the Yamanote train line in Tokyo, spending the entire day traveling around the Tokyo loop and letting people see the Walkman in action soon after its commercial release. On Sundays, they would do the same in the bustling districts of Shinjuku and Ginza, as well as at sports days and cultural festivals at local universities, stopping passersby on the street and asking them to give the Walkman a listen. Although they were met with quizzical looks at first, people's faces would light up with surprise after putting on the headphones and hitting play on the music. On the sales side, staff members at contracted retailers would walk around stores with a Walkman and demo tape, letting customers have a listen on the new machine.

In addition to these on-the-ground campaigns, ads featuring idols using the Walkman were prominently displayed in magazines, immediately raising the Walkman's name value among younger generations. These efforts began paying off in late July and August, when that first batch of thirty thousand units had completely sold out and production once again began struggling to keep up with demand. No matter how much they upped production, stores plastered with "Sold Out" signs would continue for another six months.

Half a year after sales began in Japan, the Walkman would be headed for overseas markets where, just as expected, concerns were raised about the Walkman's name. Stating that "Walkman" wouldn't work as a name since it wasn't proper English, three additional names were used for the Walkman: "Soundabout" in the United States, "Stowaway" in the United Kingdom, and "Freestyle" in Australia. When Morita traveled abroad during his business trips, however, all the people around him were clamoring for "the Walkman that you're selling in Japan right now." It seemed that the Walkman name had managed to slip out of the country and around the world. "Everybody already knows it as the Walkman. Let's keep the name," Morita decided, eventually making the naming decision public at a sales convention held in the United States in April 1980.

His decision would be proved correct - by 1986, the Walkman had become such a success that its name was listed in the Oxford English Dictionary.

As competing companies started selling their own knock-offs of the Walkman, it became clear that the Walkman had spawned an entirely new market. In the forty years between the sale of its first model and 2019, over four hundred million units had been sold, including cassette, CD, MiniDisc, and digital flash memory-based models.

The headphones that accompanied the original Walkman would continue to evolve further independently as well. In 1982, sixteen-millimeter drivers would be used to create the world's first in-ear headphone. The very first consumer noise-cancelling headphones would be put to market in 1992, followed by wireless headphones in 2017.
Although nowadays people walking while wearing headphones is an everyday sight, it can certainly be claimed that this only became a reality because of the first Walkman headphone set.