Sony has launched its á la carte download service in the U.S., along with a new version of the MiniDisc designed to take on Apple's iPod and similar rivals.

Sony has launched its á la carte download service in the U.S., along with a new version of the MiniDisc designed to take on Apple's iPod and similar rivals.

The new Sony Connect service -- a Santa Monica-based subsidiary of Sony Corp. of America -- features 500,000 tracks from all five major labels and a range of independents. Sony launched the store with a press event today (May 4) in which Sheryl Crow performed on a United Airlines flight from Chicago to Los Angeles.

Tracks cost 99 cents; most albums sell for $9.99. At launch, Connect is offering exclusive content from Avril Lavigne, Yeah Yeah Yeahs, Snow Patrol and Toby Lightman.

The European rollout of Connect is expected later this year.

In tandem with the Connect announcement, Sony has released a next-generation version of the MiniDisc, the Hi-MD. The discs have 1 GB of memory -- meaning they can hold 45 hours (roughly 675 songs) at low-quality compression rates -- and cost about $7 each. Sony also released Hi-MD Walkman digital music players, which range in price from $200-$400.

Additionally, Sony has launched a previously announced promotional deal with United Airlines that enables 44 million Mileage Plus members to earn and redeem frequent-flyer miles for Connect downloads through Mileageplusmusic.com.

Sony is coming to market as interest in digital music is on the rise. So far this year, over 33 million tracks have been sold through digital services, according to Nielsen SoundScan. Apple recently announced that it has sold over 70 million downloads through the iTunes Music Store in its first year of business.

Sony's entrance into the market also creates greater polarization among competing technology companies over formats and standards.

Connect is selling tracks in Sony's proprietary ATRAC3 format. That means music from Connect won't be compatible with music-management software and portable devices not controlled by Sony. Connect-compatible devices include the Hi-MD Walkman, the Net MD Walkman, the ATRAC CD Walkman player and the Network Walkman MP3 player. Connect tracks must be managed through Sony's SonicStage software.

Sony says it has sold more than 2.5 million Walkman-branded devices that are compatible with the Connect store. By the end of the year, the company expects that number to increase to over 7 million.