If you have a music locker on MP3tunes.com, you'll probably be glad to hear that the Web-based music storage service is adding some new features. If you are a recording company, you'll probably be upset. And if you're Michael Robertson, MP3tunes CEO, you'll regard it as one more small battle in an effort to build a business on helping music buyers control what they bought.Robertson is already being sued by one of the Big Four recording companies, EMI Group. The suit, filed in November against Robertson and another Web site he operates, Sideload.com, alleges copyright infringement. It's the same sort of suit Robertson lost some seven years ago, when his company MP3.com lost a similar suit. In a curious twist, he came out a big winner when Universal Music Group, one of the companies behind the suit, bought MP3.com for a reported $385 million. Robertson went on to launch a Linux software company, Linspire, and MP3tunes.

Robertson talked about the suit and demonstrated the new features Tuesday in an interview during the Consumer Electronics Show.

Currently MP3tunes users can manually schedule the synchronization of their locally stored music files with the contents of their storage "locker" on MP3tunes' servers. A new Autosync feature will automatically transfer files from the user's music device to their locker, and from their locker to their music devices.

Autosync uses an open application programming interface that puts the maximum functionality on MP3tunes' servers and requires as little as possible of the client devices. This, said Robertson, is part of a strategy to help users get their music on aa many of their devices as possible.

A related function announced at CES, TuneWatch, will scan users' devices for new music and sync it up to the MP3tunes servers. Autosync will appear on MP3tunes' menu in a couple of weeks, said Robertson, and as a result of a development partnership with Nokia the first mobile device to support Autosync will be Nokia's 800 series of Internet Tablet handhelds. Others, including Windows Mobile and other mobile device operating systems, will follow.

Another new feature, PlayMix, adds tagging and categorization data to users' music collections. PlayMix, based on AMG's Lasso and Tapestry technologies, will work like automatically generated playlists, so users can instruct MP3tunes to play music that resembles a particular cut, or play music with particular tags.

"One of the downsides of the locker is that if you've got a lot of music, how do you find anything?" Robertson said. "If we're doing our job right [with PlayMix] then the problem of managing your music goes away."

Robertson admits that new features like Autosynch, with their ability to spread music to even more devices, will probably draw even more fire from the music industry, but he maintains that what MP3tunes.com does is legal, and that the music companies are putting the legal rights of music buyers at risk. "We're doing the right thing with MP3tunes," he said. "The music is secure and the uses of it are legal. There's no nudge-nudge-wink-wink here, no 'oh my goodness, we didn't know letting anybody download the files was piracy.' " Even after losing the MP3.com case, which hinged on the way his site handled files uploaded by users, he still feels that he has always operated within the bounds of fair use: "What we did was fair. I defy anybody to tell me that what we did wasn't within the spirit of the copyright law."

There's something ironic in the idea that with these new features in MP3tunes.com, the better he makes it work for users the more quickly he'll face opposition from the music companies.