Though the technology looks ancient to us today, the Sony Walkman was the iPod of its time. When it was introduced to the Japanese market in 1979, magnetic cassette technology had been around for 16 years. Sony expected to sell only about 5,000 units a month, but after selling 50,000 in the first two months it knew it was on to something. Consumers loved the privacy offered by the Walkman's headphones and the convenient power source supplied by its two AA batteries, but most of all, they loved the portability. Cassette tapes made it possible to listen to music on-the-go in a way that vinyl albums simply couldn't.
Sony introduced the Walkman in the United States in June 1980, and other companies like Aiwa, Panasonic and Toshiba soon came out with their own models. While many people still preferred to listen to vinyl albums in their homes, the popularity of these portable cassette devices undoubtedly helped tapes outsell records for the first time in 1983. Cementing its place in audio history, "Walkman" entered the Oxford English Dictionary in 1986. Sony still uses the term to brand its MP3 players, but none have enjoyed the success of the original cassette player.