The deal gives Buy.com exclusive rights to sell CDs and related merchandise through MP3.com's new-music section. In return, Buy.com will open an MP3.com specialty store, featuring music downloads from its more than 40,000 artists.
"Now MP3.com fans can satisfy their tastes with mainstream music available at Buy.com and Buy.com customers can experience new music that matches their listening preferences," Michael Robertson, chief executive of MP3.com, said in a statement.
Terms of the deal were not disclosed.
The partnership comes amid speculation about MP3.com's plans to compete in the future. The San Diego-based company went public in July to stellar demand, but shares have fallen in recent months after investors began to question its revenue streams.
Launched in March 1998, MP3.com has a catalog of more than 250,000 digital song titles available for download. Users can play the digital tracks through their PCs or portable devices.
Buy.com's specialty store for MP3.com will let consumers download free music while shopping for electronics and other goods.
CNET, publisher of News.com, is an investor in Buy.com.