Apple on Monday quietly released iTunes Match, an optional paid subscription service that's part of the iCloud cloud computing services. Originally expected by the end of October, iTunes Match allows subscribers to access music they haven't purchased from iTunes via the cloud.

The theory behind iTunes Match goes like this: Users of Apple's popular iOS devices—the iPhone, iPod touch, and iPad—have music collections made up of different kinds of content. Via an iCloud feature called "iTunes in the Cloud," users have free, unfettered access to those songs that were purchased via iTunes. So they can go back and re-download them on any iOS device, or on Macs and PCs. But for those songs that were purchased elsewhere, or ripped from CD, iTunes in the Cloud can't help. So Apple created iTunes Match.

The service costs $25 per year. When activated, it will scan your entire music collection, compare it against Apple's voluminous cloud-based collection of iTunes music, and then provide you with access to clean, high-quality versions of the songs that Apple already hosts. For many users, this will be nearly their entire collection, and in my own experience testing the service over the past few months—I was in the beta—iTunes Match was surprisingly successful at duplicating my collection.

For Apple, iTunes Match makes sense because it obviates the need to force users to upload their own songs to Apple servers for cloud-based access; that type of system, used by Amazon.com and Google, would require a lot of expensive hardware and constant oversight. Instead, Apple maintains just one set of songs and provides access on a song-by-song basis to users.

For the record labels, iTunes Match appears to be a deal of sorts, too, because they would normally not ever get paid again for the music users own, regardless of how that music was obtained. So even in the case where users with illegally downloaded music collections pay the $25 fee once and then download clean, high-quality versions of their illicit collections, at least the labels are getting paid.

And for users, iTunes Match makes the most sense of all, assuming it works well. Users with legal collections are able to remotely access a high-quality version of their music from virtually anywhere without having to first upload it. And those who gave in to the temptations of illegal file-sharing services now have a way to go legit.

The question, of course, is whether it works. I'll be reviewing iCloud and the iTunes Match service in the coming week, but my testing over the past months reveals a mostly positive experience. It takes a little while for iTunes to examine and then match your collection—and I've heard that this has gotten worse with the public release, though that should ease up in the coming days—but you only have to do it once. And Apple does let you upload unmatched songs, providing complete remote access of your actual collection.

In the bad news department, this service is an obvious form of lock-in. It only works on Apple devices and software, and to access your cloud-based collection elsewhere, you'd have to laboriously re-download it first. But there's no Download All functionality, so you'll have to make playlists for downloading. I also have questions about removing unwanted songs and so on, but I'll save that for the review.

Regardless of the details, iCloud is free and well-done, from what I can see, and if you're a music fan, iTunes Match may very well put it over the top. For an Apple service, $25 per year is actually quite a deal. And even those with perfectly legal music collections should at least take a look to see whether converting those collections to something that's more accessible and of higher quality is worth the money and effort. I'm thinking it will be.

Apple's iTunes Match requires the latest version of iTunes (10.5.1) and is available now. For more information, please refer to the Apple website.