News.Com : “The software will be able to read music files encoded with ACC, a format that Apple says ‘compresses much more efficiently than older formats like MP3…

News.Com: “The software will be able to read music files encoded with ACC, a format that Apple says ‘compresses much more efficiently than older formats like MP3…while delivering quality rivaling that of uncompressed CD audio.’” [Scripting News]

And a format which is proprietary to Apple and can’t be read by any other software, I presume.