Best Buy, in cooperation with SanDisk and RealNetworks, is the latest company to join the growing list of iTunes competitors.

The company has unveiled its online music service, Best Buy Digital Music Store. It is powered by RealNetworks' Rhapsody 4.0 music service and lets users purchase songs for permanent download and also subscribe monthly to listen to an unlimited number of songs.

Best Buy will also promote SanDisk's Sana e200R Rhapsody MP3 players, which have been optimised to work with its new music service. Both the players and the service will be available starting from 15 October, the company said.

Jennifer Schaidler, vice president of music for Best Buy, said the company is differentiating its service from Rhapsody by offering exclusive artist content and tailoring that to what Best Buy customers are purchasing.

"Look at it as Rhapsody 4.0 plus," she said. "You get all the stuff that's there [on Rhapsody], plus more exclusive content."

Selling CDs and MP3 players in its stores and online is already a successful part of Best Buy's business, so offering a music service was a logical next step for the company, Schaidler said.

Songs on the Best Buy Digital Music Store will cost $0.99, with monthly subscriptions that allow users to play an unlimited number of songs for $14.99 a month.

The news follows Microsoft's announcement of its Zune Player and Zune Marketplace service, which also sells songs and subscriptions at the same prices.

The SanDisk Sana e200r MP3 players come in two models - a 2GB model for $139.99 and an 8GB model for $249.99. It also includes an FM radio tuner and plays music, photos and videos.

To promote its new service, Best Buy will launch with an exclusive track from recording artist Diddy from his new CD, Press Play. The CD will be on sale 17 October.