Sony engineers said nobody would buy a playback-only tape player — the Walkman sold 400M

In the late 1970s, Sony co-founder Masaru Ibuka frequently traveled with the company's bulky TC-D5 cassette recorder just to listen to music. He asked the audio department to build a smaller, playback-only version he could take on flights. The engineers were skeptical: the device could not record, and they could not imagine who would buy a tape player without recording capability.

Despite the internal resistance, Ibuka persisted. The audio department modified the existing Pressman recorder (a compact device for journalists) into a playback-only stereo model. In March 1979, Ibuka tested the prototype and was pleased with the sound quality. Co-founder Akio Morita, seeing the prototype, pushed for a full launch. He famously predicted the product would sell 5,000 units per month.

The Sony Walkman TPS-L2 launched in Japan on July 1, 1979, priced at approximately ¥33,000 ($150). It was a blue-and-silver metal case with a headphone jack, no external speaker, and no recording capability — exactly what the engineers had warned against. Morita positioned it in the youth market, emphasizing vitality and fashion. In the US, it was initially called 'Soundabout' because the name 'Walkman' was thought to be awkward English.

The Walkman sold more than 30,000 units in its first two months — six times Morita's prediction. By 1983, cassette sales had overtaken vinyl records for the first time, largely driven by the Walkman. The word 'Walkman' entered the Oxford English Dictionary in 1986. By 2010, cumulative sales of all Walkman devices reached approximately 400 million units. The product that engineers said nobody would buy had created the portable music market.