Back in 1979, Sony cofounder Masaru Ibuka was looking for a way to listen to classical music on long-haul flights. In response, his company’s engineers dreamed up the Walkman, ordering 30,000 units for an initial production run. Forty-five years later, Sony has sold over 400 million Walkmans and incited a revolution in music technology.

While there are still Walkmans for sale, most use iPhones and Androids to tune in nowadays. Sony Walkman sound engineer Sato Hiroaki, who joined the company in 1986 while the device was at its peak, sees remnants of the Walkman in our present listening patterns. “To this day, I still see the simplicity and user centric design of the Walkman in portable music products,” Hiroaki writes to Fast Company in an email. “Every time I see someone listening to music on their headphones, I think of the initial introduction of the Walkman, and how that got us to where we are.”

The Walkman’s early days

Forty-five years ago, Sony’s then-president Norio Ohga took up Ibuka’s call for a transportable listening device. He asked an engineer to turn the company’s Pressman tape recorder into a playback-only stereo device. The resulting model was clunky: Headphones then were heavy enough to keep the listener stationary, and custom batteries limited marketability. But slowly, Sony slimmed the product enough for mass production.

“[It] freed listeners from the confines of their living rooms,” Hiroaki writes. “In order to do this, original engineers made the decision to remove the recording functionality and forgo an embedded speaker, and added stereo playback circuitry in the available space to make the player more portable—a decision that ended up creating a whole new product category.”

The original model, the TPS-L2, was a mere 5 x 3 inches, small enough to hold in the palm of your hand. It also only had one use: To feed the audio from a cassette tape into the attached headphones. But that alone was technologically innovative, especially in a time when stereos blasted muffled radio static into the open air.

“It was impressive at the time, because you’re hearing it piped directly into your brain, as opposed to ambient sound,” says Mark Katz, a music professor at the University of North Carolina, Chapel Hill.

Sony produced an initial 30,000-unit run of the TPS-L2. Only 3,000 sold in the first month but, through word of mouth, it spread. By the second month, that run had sold out, and batch sizes were upped to meet rising demand. Sony entered a golden era, where sales skyrocketed and brand caché grew. In just a year postlaunch, Sony’s U.S. sales grew 41.3%. Within five years, they were making $6.7 billion worldwide.

While the launch’s success may look fated in hindsight, Sony took a major risk taking such a nascent product to market. In his book The Wide Lens, Dartmouth College’s Ron Adner details how being “first” isn’t always the smartest. Consider the adjacent MP3 boom: While dozens of companies (including Sony) pushed out devices, it was Apple’s iPod that captured the market three years later. Sometimes holding back is better—but not for the Walkman.

“The market really does appreciate great execution, and getting the right idea right can give you a tremendous first mover advantage,” Adner says. “The risk of being a first mover is [that] you’re going to get it wrong. Somebody else is going to learn from your mistakes. . . . The lesson for entrepreneurs from the Walkman is: There’s what it looks like when you have the right insight delivered in the right way.”

A revolution of personalized listening

Solo listening wasn’t always the norm. Before the Walkman boosted cassettes to top status, vinyl records were all the rage, though they were expensive and cumbersome. Their players, of course, were even bigger. Stereos simplified the listening process, but they, too, were large and loud. This all meant music was heard with friends and family, and rarely by oneself.

“In the ‘70s, when I was in college, guys would have these big, expensive stereo systems, and every other room in a dormitory would be blasting out a different kind of music,” says Mark Coleman, author of Playback. “Music became a much more personal thing.”

This communal listening model proved difficult to shake. For the first few years, Walkman listeners were scoffed at for their colorful headphones and propensity to walk into traffic. The TPS-L2 even had two headphone jacks, just in case listeners wanted to plug in with a friend.

“Listening to music by yourself was seen as antisocial,” says Katz, the UNC professor. “Back then, it seemed actively transgressive that someone would decide to close themselves off from the world, especially in public places.”

By now, the culture has flipped. Private listening is the norm, with public listening reserved for concerts and ambient soundtracking. Walk the streets of any major city; you’ll see glaring white AirPods, only a touch more reserved than those original Walkman headsets. Only now, we’re not making fun of those who walk around with AirPods in.

Neal Manowitz, president and COO of Sony Electronics, remembers his Walkman fondly. Whenever he hears Asia’s “Heat of the Moment,” he thinks back to the ‘80s, when he’d blast the song on his WM-4 device. While he’s proud of Sony’s push towards private, personalized listening, he emphasizes that the Walkman still had more neighborly functions.

“With the creation of ‘mixtapes,’ people could now curate their own set of songs to hear in whatever order they wanted (rather than listening to the radio) and take it on the go,” Manowitz writes in an email to Fast Company. “[It brought] people together through the sharing of music, without having to be in the same room. Behavior we take for granted today, like creating a playlist online, was revolutionized during the peak of the Walkman.”

The Walkman still looms large

After 45 years, Sony is still defined by the Walkman. Their mid-’80s bump awed the entire market, inspiring later visionaries like Steve Jobs, who fashioned Apple after the company. Even now, as Sony’s stock climbs to record high’s, everything is still compared to that infamous era. CNN’s headline: “Sony hasn’t been this hot since it made the Walkman.”

“The Sony brand has always been synonymous with entertainment fueled by technological innovation. With Walkman, the brand immediately gained cultural cache as well,” Manowitz writes. “The brand was no longer just ‘good tech,’ it became a symbol for personalization, creation, and self-expression as well.”

The Walkman didn’t just help Sony; it also spun off dozens of companies and industries in the music tech area. The headphones market is now crowded and moneyed: Apple, Bose, and indeed Sony fight it out for market share. But, before the Walkman, these devices were mostly frowned upon.

“In the ‘70s, if you were sitting around listening to music on headphones, you were identifying yourself as a nerd or a stoner,” says Playback author Coleman. “Headphones became much more common then.”

The Walkman isn’t dead. Since 1979, Sony has rolled out over 1,000 models of the device. Hiroaki details this progression, moving from cassettes to CDs to dropping physical media altogether. They’ve also added a touch screen, wireless capability, and some new AI functions. But some things have stayed the same: “I believe that the idea of listening to one’s favorite music in one’s favorite place with good sound has remained unchanged since the first-generation Walkman TPS-L2,” he writes.

Holding the new-age Walkman can be a bit jarring. Its design is entirely different, turned into a pseudo-iPhone that can even browse Google Chrome. But, plugging in a nice big pair of headphones, there’s something refreshing about the device. As streaming blurs music, podcasts, and videos, and as the music market is continually warped by TikTok, it’s nice to hold a device solely devoted to pure-form listening. Now, the Walkman is nostalgic; 45 years ago, it was revolutionary.