When you want to hear music while you're out, you just pop in the earbuds (or just tap them because they're embedded in your ears already), and summon the song on an app like Spotify or Apple Music and listen. You probably don't think too much about it.

But a generation ago, if you wanted to listen on the go, you very likely did it through a Sony Walkman. It's what made cassette tapes (the MP3s of the day) portable. Why talk about old tech? Because it's where getting your groove on the go started.

In early 1979, Sony chairman Akio Morita summoned apprehensive young, engineers, planners and publicity people to a meeting to show off a promising prototype, a modified version of a compact cassette recorder used by journalists known as the Sony Pressman.

"This is the product that will satisfy those young people who want to listen to music all day,” Morita told the group. “They'll take it everywhere with them, and…if we put a playback-only headphone stereo like this on the market, it'll be a hit."

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On July 1, 1979, Sony launched the blue and silver Walkman TPS-L2 in Japan and sold it for around ¥33,000, roughly $150 at the time in U.S. dollars. A year later, it came to the U.S.

Despite skeptics who predicted this expensive device wouldn’t sell because it didn't record, that first Walkman became a blockbuster hit, selling 50,000 devices in two months. But more than that, it changed the way people listened to music privately and portably. Remember, carrying around your favorite tunes had been a back-breaking endeavor that spilled over to everyone around you. This was the era when boomboxes were big -- literally.

Among the Walkman's early features was not one but two earphone jacks so that you and a friend could listen at the same time.

“The Walkman did a couple of things in one,” tech historian Stewart Wolpin says. “It was the size of a transistor radio but was so much easier to carry than previous tape-based portables. And more importantly, it came with stereo headphones designed for music, not that mono earpiece for the transistor radio. The music sounded like you’d brought your home stereo with you, and it was yours and yours only. The headphone stereo phenomena defined the indulgent, some would say selfish, 'Me' generation of the 1980s.”

Much to Sony’s chagrin, the Walkman brand also became the generic stand-in for all the rival portable music players of the day, just as Kleenex brand came to define boxes of tissues.

Through the years, Sony brought out numerous variations of the Walkman: portable CD models, “gum-stick” versions with a rechargeable battery, and models that supported “metal” tape, and mostly forgotten formats – unless you’re a tech nerd – such as DAT (Digital Audio Tape), MiniDisc and “Duo” Memory Stick.

Some models were waterproof, some were compatible with High-Res Audio, and some even played video.

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Sony eventually went with models that could handle MP3s as well, but it was late to the game. In the new century, the company relinquished the portable music throne to Apple's iPod and iTunes.

Looking back, Wolpin says Sony’s boss Sir Howard Stringer had completely siloed the company’s divisions so that the electronics business was kept separate from Sony's recording and film divisions.

“This kept Sony from building an iTunes/iPod-like integrated music player/music store solution," he says. "Sony would have been the only potential competitor to Apple had the Sony hardware and Sony content people been able to talk to each other.”

On its 40th anniversary, the Walkman is a faded brand, but one that still conjures up mostly fond memories to a certain generation.

What was your first mobile music player – a Walkman, an MP3 player like an iPod or your smartphone?

Email: ebaig@usatoday.com; Follow @edbaig on Twitter