(AP) -- This year marks the 40th anniversary of the Sony Walkman first portable cassette player.
The TPS-L2 was a breakthrough in portable technology that changed the way people listen.
Forty years ago, Sony debuted the Walkman, a portable tape player that delivered music on the go.
But thanks to this small metallic blue personal stereo cassette player, the way in which we listen to music today was revolutionised.
It would be hard not to find at least one train carriage with a commuter plugged in or a gym-goer enjoying their upbeat running playlist.
Today you can still listen one to any one of your favourite songs from the British Band, The Beatles, on a Sony device.
Albeit a version far more advanced than the 1970's classic cassette player.
Director of the Museum of Portable Sound, John Kannenberg, explains: "the original Walkman had something called hotlink technology, that's what they called it. Which was...it consisted of two headphone jacks so that two people could listen to it at a time and a microphone that didn't actually record onto the tape. But the microphone existed to pick up the sounds of the voices of the listeners so that they could speak to each other without taking their headphones off."
In an iconic advert, the Walkman was shown off by a skateboarder to illustrate how the portable cassette tape player delivered music on the go.
By 1986 the word "Walkman" was added to the Oxford English Dictionary.
Over the next ten years, the cassette player was updated to include an FM stereo, belt feature and a twin tape deck.
In 1984, the WM-F5 was released, Sony's first "Sports" Walkman model.
Its launch coincided with 80's aerobic craze. Many would use the Walkman to make their workouts entertaining.
"One of the things that the Walkman did during the 80s was it sort of took exercising too to a new public level. So people would use the Walkman to provide a soundtrack for jogging or aerobics and they could do this outside of their own homes. So it led to the sort of a new culture, a new add a new layer of culture, when it came to things like jogging and public forms of exercise," says Kannenberg.
At the time Sony Corp. co-founder Masaru Ibuka was tired of lugging the TC-D5 cassette deck while travelling for business and wanted something smaller.
Only transistor radios were portable, but there was nothing widely available like the Walkman.
Sony designer Norio Ohga came up with the prototype of something much smaller.
The Walkman unit from 1979 - the TPS-L2 was the first personal stereo cassette player to be made commercially available at a price tag of $150.
Originally called the "Soundabout" in the United States and the Stowaway in the UK, in the early 1980s the Walkman caught on globally.
Along with the miniaturization of the Walkman, there were great feats in headphone technology too.
The headphone jack made it an ideal product for taking your portable stereo on the go.
In 1984 the Walkman had a portable CD player successor, Sony's Discman, the first model being D-50.
It continued to transform with the ages over the years into the Mini-Disc and MP3.
But the music cassette player that was ground-breaking in its day eventually dwindled to a tiny niche in the era of digital technology.
In 2001 something came onto the market that changed the way we listen to music.
Apple's iPod, it was the first listening device that would allow you to upload songs digitally.
Unable to keep up with the digital age, Sony announced in 2010 it would stop selling the Walkman cassette player.
John Kannenberg, Director of the Museum of Portable Sound explains technological advances led to the demise of the Walkman.
"One of which was cassette, tapes themselves became sort of obsolete. On the arrival of the compact disc first, and then, the final nail in the coffin was really the iPod. Once music became digital all of the sort of technical advances that had been so significant when the Walkman was first released sort of faded away. It was no longer just good enough to listen to a cassette on the go."
This was the first generation of water-resistant players, the WM-F63 (1986), and it featured in the 1990's blockbuster Pretty Women.
While Julia Roberts sang in the bathtub to the lyrics of 'Kiss' by Prince, the small yellow Walkman in the background was dangerously close to the edge.
Its tough exterior also proved to be a handy jogging accessory.
As for the future, Kannenberg explains, "I'm really not sure what...what kind of future there is for the Walkman. Although there is there's quite a resurgence of audio cassettes in sort of underground music culture at the moment. So the Walkman could make a slight comeback at least in a very underground way."
Sony continues to produce the Walkman brand but as a digital music player.
And in the 21st century, the Sony Walkman has come a long way.
With prices ranging from £110 to £2500. The top of the range, WM1A Walkman, can play music for up to 45 hours between charges with over 125 GB of memory built in.
Sony sold more than 220 (m) million cassette Walkman players globally since the product's first model, the TPS-L2, retailing at 200 US dollars.
With the increasing sales of smartphones, portable media players have been largely phased out.
But the legacy remains the same - listening to music whenever and wherever.