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Today marks the 40th anniversary of the Sony Walkman, a piece of technology that not only rocked the recording industry, but fundamentally changed how we all experience music. For the first time, you could pop a cassette tape into a portable player and listen on the move.

But the story of the Walkman is also a cautionary tale for brand owners. You can have the whole world of technology in your hands – but fail to keep up with where the market is going next. The Â鶹ԼÅÄ's Nigel Cassidy showed a Walkman to two sisters, aged 9 and 11, to see if they could figure out how it works.

(Image: A 1980 Sony Walkman 'Stowaway TPS-L2. Credit: Getty Images)