Microsoft appears to finally be going after the growing digital music market with a planned release of a public beta of its MSN online music service.

Details of this offering are still sketchy, but more information should be available later this week with the official launch of this public beta. Microsoft is likely taking aim at Apple’s iTunes. The Microsoft music store promises to set up a head-to-head battle with Apple that recalls their rivalry in the personal computer business.

Unlike Real Networks, who created controversy by engineering its online music store to work with Apple’s iPod, Microsoft will emphasize that songs downloaded from MSN will play on a reported 60 players, but not on the iPod. Microsoft doesn’t make its own hardware and will use a “Plays for Sure” slogan that can be put on devices so buyers know they work with multiple services.