The biggest player in digital music has finally vaporized its content. Starting this fall, you'll be able to store your digital music library on Apple's internet servers. We've already seen Amazon and Google's attempts at a Web-based music service, with the former's Cloud Player and the latter's Google Music Beta, but with iTunes' dominance in digital music, Apple's iCloud could eclipse both of them. Apple's offering differs from those of Amazon and Google in some big ways, though. Here's a rundown of the three services' differences and similarities.

A central difference of Apple's iCloud versus the others is that it's not just for music: It takes over all the former MobileMe's functions—email, contacts, calendar—along with backing up and syncing iOS device photos, app data, and iWork documents. Thus ends the stormy story of the MobileMe service, which even Steve Jobs noted at WWDC was "not our finest hour." This comparison, though will concern itself primarily with the music aspect of iCloud, iTunes in the Cloud. This piece is available as a beta by downloading iTunes 10.3.

A huge difference of iCloud's music capabilities is that you can't play songs from within a Web browser (at least as far as we have seen so far) as you can with both Amazon and Google's offerings. You'll either need an iOS device or iTunes running on a computer. True, this does include Windows PCs running iTunes, but forget any non-Apple tablets or phones. This lack of Web access is just less flexible. Nor can you stream music from its online storage—the music must be fully downloaded to play.

One point strongly in Apple's favor, though, is how you get music up to the cloud. With Amazon and Google, you have to wait for the actual data to upload from your computer or device, which can take many days if you have a large music collection. Apple, by contrast, has high-resolution (256 kbps AAC) versions of 18 million tunes already stored on its servers, so once iCloud checks that you own a song, it uses that copy for future downloads. This means no wait for lengthy uploads, and keep in mind that even broadband connections usually have much slower upload speeds than download speeds.

Apple has reportedly made deals with the four major music labels--Universal Music Group, EMI Group, Sony Music Entertainment, and Warner Music Group to make this online copy possible. Amazon and Google have taken a different approach, considering the online music locker as simply another storage device, like a hard drive in the sky.

Recommended by Our Editors

Wikipedia Editors Could Strike Following Layoffs

Blue Origin’s New Glenn Rocket Explodes Spectacularly During Ground Test

Google Engineer Charged for Using Insider Info to Win $1.2M on Polymarket Bets

Then there's the matter of buying new music. Of course, Apple excels in this area, with iTunes offering the largest digital library with 18 million songs. Amazon isn't far behind, though, with 16 million. Any digital music you buy from Amazon will automatically enter into your Cloud Player, and you won't have to pay for its storage space—the same goes for iCloud. Google has yet to announce music buying capability—a serious drawback to its streaming music ambitions so far.

And what about old music you didn't by through the service? Apple has a unique approach here, as well, with what it's calling iTunes Match. The other services don't care where you got your music, you can upload it to them regardless of source. But with iCloud, you must pay $24.99 a year for non-iTunes-purchased music to be stored online. The good side of this is that once you pay that annual fee, you won't have a storage limit. And another benefit is that your tunes will be replaced with the high-resolution copy if they're not already at that quality level. A downside is that you'll have to pay the fee even if you have just a few non-iTunes-purchased albums.

Those are the biggest differences. For some more fine-grained differences, you can peruse the table below. In all, the three online music services vary widely, and as you might expect, the one from Apple is in many ways the most polished and full-featured—with one possible exception: it seems pretty clear there isn't going to be a Web interface for playing music. But iCloud won't be available until fall; we hope this changes? If nothing else, though, the new iCloud feature makes getting your iTunes music on multiple devices and computers a lot simpler than the old USB syncing method.