For smartphone users and iPod fans carrying around thousands of songs, the excitement and mass consumer demand that greeted the Sony Walkman when it launched in 1979 is hard to imagine. But this cassette player was the first commercially available portable personal stereo with earphones.

Not all the technology was new, magnetic cassettes had been around since the early 1960s and Sony was at the time expert at miniaturising electronic gadgets. But this portable blue and silver sound system with its chunky buttons – in its leather case – offered users good quality audio and the privacy of headphones. It had two headphone jacks in case you wanted a friend to also listen to your favourite tunes; it had no external speaker. In the US it was called the Soundabout and the Stowaway in the UK until Sony firmly established it as the category defining Walkman. (In 1986, Walkman entered the Oxford English Dictionary.)

It was designed after Masaru Ibuka, Sony’s co-founder, tired of lugging around a cassette recorder to listen to music while away on business trips, commissioned Norio Ohga to design a playback stereo with headphones that could be used while walking around. At the time prerecorded cassettes were edging out with vinyl the preferred way to listen to music.

As its origins were almost a personal project, Sony had modest ambitions for the Walkman, expecting sales of about 5,000 a month on its Japanese launch. It sold 10 times that and went on to sell an estimated 200 million in its various iterations.