'Napster To Go' allows for transfer to devices.

Napster today (Sept. 1) became the first digital music service to jump into the subscription portability business, launching a preview of an offering called "Napster to Go."

The service -- which is based on Microsoft's new Janus digital rights management technology -- is rolling out in conjunction with Microsoft's launch todayof the MSN Music download store and an updated version of the Windows Media Player.

Napster to Go, which at launch costs $14.95 per month, allows subscribers to transfer any songs in the Napster subscription library to a Janus-compatible device.

The price is subject to change with the official launch of Napster to Go later this fall. Labels and music services are still trying to determine a proper price point for music that consumers rent access to but don't own. With the existing Napster service, users can either buy permanent downloads for 99 cents each or $9.99 an album, or pay $9.95 per month for an unlimited amount of music that cannot be moved off the computer.

"We are putting our stake in the ground as the market leader by introducing this highly anticipated and game-changing capability in preview and look forward to offering music fans its modified and enhanced final version in our updated client this fall," says Napster chairman/CEO Chris Gorog.

Initially, only the Creative Zen Portable Media Center and the Samsung Portable Media Center -- which cost around $500 each, and are expected to become available for purchase in the coming weeks -- will be compatible with Napster to Go. An expanded range of compatible players from Creative, Samsung, Rio and iRiver is expected to hit the market later in the year.

Under the subscription portability rules, consumers must verify that they have an up-to-date subscription with Napster by connecting the portable device into their computer at least once every 30 days, or they will not be able to play back the music.