It's the summer of the cloud! With new details of Apple's forthcoming cloud music service leaking out, it's an opportune time to survey the landscape of the major three players in the cloud music market: Amazon's Cloud Drive, Google's Music Beta and (expected at next month's Worldwide Developers Conference in San Francisco) Apple's cloud music service. Each boast slightly different features with different options for purchasing music or uploading your own collection. Here are the important contrasts:

Amazon's Cloud Drive

First to market in March, Cloud Drive gives every user 5 GB of free storage space of their music, charging $1 for each additional GB. Albums purchased on Amazon's huge MP3 Store are stored for free and the first purchase of an album awards users with 20 GB of free storage space. It's compatible with Macs, PCs and Android phones via Amazon's MP3 App but not the iPhone (though there are clunky workarounds for those). Cloud Drive was not unveiled with the blessing of music labels and questions of its legality loom, as with Google's Music Beta service. Reviews of the service thus far have been mixed. The New York Times David Pogue loved it. "The Cloud Drive/Cloud Player is beautifully done, rock solid in operation and every bit as convenient as Amazon promises," he said. Meanwhile, All Things D's Peter Kafka echoed complaints from others in the tech press. "Cloud music could become really interesting, if it also allowed you to listen to music your friends owned or liked, or turned you on to music you’ve never heard before," he said. Since Amazon's doesn't, he said it "isn't earth-shaking."

Google's Music Beta

Currently invitation only (sign up here for an invite), Music Beta is a free music locker service that allows users to upload 100 gigs of music or about 20,000 songs—way more than Amazon offers.. As with its competitor, it uploads your music directly from iTunes. "If you have more than 20,000 songs in your iTunes account, Google says it will first upload your iTunes account’s frequently played songs, favorites and starred music," explains Wired's David Kravets. "Then it uploads in alphabetical order from the first name of a band or artist until you max out on space."  Like the Cloud Drive, it's compatible with Android phones but does not offer support for the iPhone. Another common complaint about Google and Amazon services is that the upload process is slow. The main thing Music Beta has on Amazon is its initial generosity of 20,000 songs for upload. However, unlike Amazon, it doesn't give you the option to buy a bigger locker (at this point anyway).

Apple's "iCloud" Service

Threatening to really undermine the competition, Apple's music service will reportedly have the blessing of major labels including EMI, Warner Music and Sony (Universal continues to be a holdout), reports BusinessWeek. Unlike its two competitors, slow upload speeds won't be as much of a problem. "Apple's 'iCloud' service will automatically add tracks that are in Apple's extensive iTunes Store library," reports Ars Technica. The service will "scan customers' digital music libraries in iTunes and quickly mirror their collections on its own servers." If the songs aren't available on iTunes, they'll have to be uploaded but the feature will definitely speed the whole process up. Another benefit for audiophiles will be the sound quality, reports Ars. "Users will be able to stream iTunes Plus versions of the songs, even if the user originally encoded the tracks as lower quality AAC or MP3 files," writes the website. "Such a feature was also a benefit of Lala, the streaming music service Apple bought in late 2009." Those major features may give music fans pause when facing a time-consuming upload of their entire music collection to Amazon and Google.