In 1982 the mayor of Woodbridge, New Jersey, banned pedestrians from wearing portable cassette players in public. The device behind the panic had started as one executive’s complaint. Sony co-founder Masaru Ibuka was tired of hauling the bulky TC-D5 recorder on long flights to hear classical music, so he asked Norio Ohga for a playback-only machine. Engineers gutted a dictation recorder called the Pressman, added a stereo amplifier, and on July 1, 1979, launched the blue and silver TPS-L2 in Japan for about 150 dollars.

This episode follows the Walkman from that prototype to a word in the dictionary, and then to a cautionary tale. Under Akio Morita, Sony sold a lifestyle rather than a tape deck, putting headphones on strangers in the streets of Tokyo. The private bubble it created reshaped public life and exercise habits. Yet the company that taught the world to carry music released a digital player two years before the iPod and still lost.

• Inventor Andreas Pavel had imagined a wearable player he called the Stereobelt, and his legal fight with Sony ran until a 2004 settlement reported as a low eight figure sum plus royalties.
• Overseas divisions disliked the name, so early units sold as the Soundabout in the US, the Stowaway in the UK, and the Freestyle in Sweden and Australia.
• Sony expected to sell about 5,000 units a month and sold over 30,000 in the first two months, and cassettes passed vinyl record sales by 1983.
• The Network Walkman of December 1999 required Sony memory sticks, the ATRAC format, and OpenMG copy protection, a choice driven by fear of piracy at the company’s record label.
• By 2006 Sony held just 1.9 percent of the U.S. market, but the brand lives on in luxury players, including a gold-plated model priced above 3,200 dollars.