By the late 1980s, audio cassettes were being displaced hard by CDs. Sony began to develop the Minidisc in 1986 as a next-generation portable audio device.
When Sony introduced the Betamax video format in the 1970s, they kept it a closed standard. This led it to fail on the market against the open VHS standard, because far more companies were producing VHS material. Sony learned from this with the Minidisc, and licensed the technology to other manufacturers such as JVC, Sharp and Panasonic.
The Minidisc was launched in 1992. It met with great success in Japan but had lackluster reception in the United States, where fewer than 50,000 units were sold in its first year. In an attempt to overcome this, Sony reduced prices and launched several major, but unsuccessful, marketing campaigns.
The Minidisc came on the market at a time when several competing formats were also being introduced, such as digital compact cassettes. Later in the 1990s, recordable and rewritable CDs came onto the market, further diminishing the Minidisc's market share.
The first commercial MP3 player, the Diamond Rio PMP300, was released in 1999. While the Rio itself wasn't extraordinarily impressive, successive MP3 players--such as the iPod, released in October 2001--were faster and better. Digital audio players have come to fill the next-generation-portable-music-player niche that Sony intended the Minidisc for.