The once-dominant force in portable music formally ceded ground this week to the current boss of the digital music game.

Sony's Sonic Stage with Connect store.

Sony, the Japanese giant that once controlled the portable music market with its ubiquitous Walkman players, has confirmed that the latest version of its music management software will support the AAC file format used by Apple's iPod/iTunes juggernaut.

Sony said its update of Sonic Stage music management software would be compatible with songs ripped from CDs into iTunes in the AAC file format. The move doesn't affect songs purchased from the iTunes Music Store, as Apple uses its FairPlay digital rights management (DRM) technology to prevent iTune-purchased music from playing on anything but iPods.

But the move marks a departure from Sony's strategy--like that of Apple and Microsoft's Windows Media--to only allowing compatibility with its proprietary Atrac file format.

"That's a big change for Sony," American Technology Research analyst Shaw Wu told CNET's News.com. "But it's not surprising. Competitors keep trying to stop Apple, but the company's market share just continues to grow."

] The new version of Sonic Stage is expected to be available as a free download by May 25, Sony said, and will also include compatibility for songs ripped into the Windows Media and MP3 formats.

SonicStage has been around since the first Walkman-branded digital music players shipped in the late 1990s, and Sony encouraged its users in January to use Sonic Stage instead of ConnectPlayer if the newer software caused instabilities on the users' PCs.