The songs will be sold in MP3 format, which means users of the Rhapsody service will be able to play them on iPods.
Before now Rhapsody, jointly owned by Real Networks Inc and Viacom Inc's MTV Networks, had focused on a subscription service, allowing unlimited song streaming for $13 to $15 a month, rather than selling downloads.
But Rhapsody Vice President Neil Smith said the fact the service has not been compatible with Apple Inc's top-selling iPod digital player has limited Rhapsody's reach.
"We're no longer competing with the iPod," Smith said. "We're embracing it."
Rhapsody also will be the music store back-end to MTV's music Web sites and iLike, one of the most widely used music applications on social networking site Facebook.
Rhapsody will be available on mobile phones via the Verizon Wireless VCAST Music service. Buyers of a song over-the-air directly from phones also will be able to download that song to their computer. Verizon Wireless is a joint venture of Verizon Communications Inc and Vodafone Group Plc.
Rhapsody executives describe the strategy as "Music Without Limits." They said it would be backed by a marketing blitz worth up to $50 million in media space over the next year in part by leveraging co-parent MTV's TV networks and Web sites.