Wikipedia
The Stereobelt was the first portable personal stereo audio cassette player. It was invented by the German- Brazilian Andreas Pavel. The Stereobelt was the ancestor of the Walkman and later personal audio devices such as the iPod.
A former television executive and book editor, Pavel invented the Stereobelt to "add a soundtrack to real life" by allowing the user to play high-fidelity music through headphones while participating in daily activities.
The initial test of the device took place in February 1972 in St. Moritz, Switzerland, when Pavel pushed the play button to start the song " Push Push" by Herbie Mann and Duane Allman. Pavel experienced a "floating" sensation as he listened to the music and watched the mountain snow fall, realizing that his new device could provide "the means to multiply the aesthetic potential of any situation."
Pavel approached electronics manufacturers such as ITT, Grundig, Yamaha and Philips with his invention, but the companies felt that no one would ever want to wear headphones in public for listening to music.
Frustrated with his lack of progress, and learning that it was important to protect his idea, Pavel finally filed a patent for the Stereobelt in Italy in 1977, followed by patent applications in the U.S., Germany, the United Kingdom and Japan by the end of 1978.
Sony began selling the arguably similar Walkman personal stereo in 1979. In negotiations that began in 1980 and ended in 1986, Sony agreed to pay Pavel limited royalties for the sales of certain Walkman models sold in his home country of Germany only.(about 150.000 deutsche Mark, almost 1% of Sonys Walkman profit in Germany)
A second round of legal battles between Pavel and Sony that began in 1989 in Great Britain ended when the case was dismissed in 1996, leaving Pavel to pay more than $3 million in court costs.
Finally in 2003, with Pavel threatening to file infringement lawsuits in the other territories where he holds patents, Sony agreed to settle out of court, which led to both parties signing a contract with confidential content in 2004. The settlement was reported to be a cash payment of over $10,000,000 and ongoing royalties of the sale of certain Walkman models.