We've all been there: you've rushed out the door and realized you've forgotten to sync your phone. You were really looking forward to listening to that new album on the way to work, but now you'll have to settle for talk radio, or worse, an album you've already played out.

The introduction of cloud music storage makes this small problem an issue of the past. With services like iTunes Match, you can simply purchase or upload an album and have it available on all your iOS devices in an instant for $24.99 a year. As an added bonus, you can also save space on your hard drive by permanently storing all of that music on Apple's servers, which helps if you're downsizing to smaller computers with flash storage or hopping from computer to computer without a permanent place to keep your music. Cloud storage is now an essential component for music libraries, and although it hasn't completely eliminated the need for hard drives and local libraries, it's certainly made it easier for users with mobile lifestyles.

Apple isn't the only company to provide this type of service. Google and Amazon also offer similar cloud-locker music storage services. Amazon switched to scan-and-match after a year of offering purely storage and streaming for its users, while Google Music recently tweaked its upload-and-stream service to allow users to do more than just store music files. Both services come with most of the same features as iTunes Match, and Amazon's service costs as much as Apple's per year while Google Music is completely free.

With all of this choice, it raises the question of which service to use. Does Google's completely gratis scan-and-match service win out over Amazon or Apple's paid offerings? Does Amazon's Cloud Player offer something over iTunes Match that Apple may never be able to offer? Or is sticking with Cupertino the way to go?

How do they work?

First, let's break down what all three scan-and-match services offer and how they work. After you import your music into iTunes, iTunes Match will effectively scan the music in your library and either upload it to the cloud or find a match for it on its servers. Google Music, on the other hand, requires that you use the Google Music Manager before it gets to work. You'll need to point the app to the location of your music library—whether it's in Windows Media Player, iTunes, or some other folder on your hard drive—and the Music Manager will begin to scan those files and look for existing matches in the cloud, or upload them directly if they do not exist. Amazon's music service is native to the Kindle Fire and is thus known as Amazon MP3, which is how you'll find it in the iTunes App Store and Google Play. The service stores any DRM-free music previously purchased through the site. It recently updated its service to include the tracks from any physical discs you purchased from the site after 1998.

Google Play allows you to keep up to 20,000 songs stored on Google's servers, while Apple’s iTunes Match stores your entire music library in iCloud and matches up to 25,000 tracks (though as we explained in our previous examination of iTunes Match, songs purchased from the iTunes Music Store don't count toward your 25,000 song limit). Amazon's cloud locker service, dubbed the Cloud Player Premium, features two tiers: the free version allows up to 250 imported songs, while the premium version costs $24.99 a year but enables subscribers to upload 250,000 imported tracks. Neither of these limits count toward purchases that were made from Amazon MP3 directly, or those old CDs you might actually rather forget you ever purchased.

Google Music won’t retroactively match your existing library if you uploaded music to the service before the scan-and-match feature was announced—at least not yet. According to its official Google Play FAQ page, it will automatically match songs “in the next few months.” Any music that you upload now, however, will be matched as it’s available. If you'd like, and you have the patience, you can delete your music library and subsequently re-upload it to have it all matched.

Once your music is stored in Google Music, you can listen to it on the Web or via your mobile device—this includes both Android and iOS devices, though the latter is only accessible via an HTML 5-rendered webpage. In iTunes Match, music is accessible through all iOS devices, as well as through the iTunes desktop client. With Amazon Cloud Player, you can access your collection on the Web or via an iOS or Android app.

How can Google Music be free when iTunes and Amazon are charging an annual fee? According to the Wall Street Journal, Apple and Amazon's strategies are to use the subscriber fee to pay for the payments to the music labels and publishers in order to match some of the songs that may be pirated—often referred to as a "sin" tax. Google, on the other hand, has simply decided to foot the bill by digging into its own pockets.

Uploading

All three services require a desktop component to help upload the music directly to the cloud. Google requires you to download the Music Manager application, while iTunes Match syncs with iTunes. Google’s Music Manager can scan various applications for new music, including iTunes and Windows Media Player on the PC. iTunes Match requires the song to be imported into the music library or purchased from the iTunes Store before it does the sync or match.

Amazon requires you to download the Amazon Music Importer, which is essentially a browser plug-in for Internet Explorer, Firefox, and Safari. Google Chrome users are out of luck here because, according to Amazon's FAQ, newer versions of Google Chrome do not fully support the latest iteration of Adobe Flash Player. You'll also need Adobe AIR installed to get the Music Importer to work with your browser.

By default, the Amazon Music Importer app extracts data from your iTunes or Windows Media Player libraries, though an option to manually sift through your own folders on your hard drive is available. Once you hit go, Amazon will proceed to upload and match any file it can from your library.

Uploading to all services is relatively simple, but determining what music has been uploaded or matched can be puzzling, particularly in Google Music. In iTunes, you can right-click on the menu bar and select “iCloud status” to determine whether a song has been matched or uploaded. Google Music is a bit trickier to figure out since the music player is mostly Web-based. Several users have noted that a good rule of thumb for checking what songs were matched is to check whether Google will link you to the Play store from a particular album or song, but that’s not always a sure bet. We also tried to test what was uploaded by downloading songs to see if the bit rate had been matched in the cloud. Eventually we figured that if the track offered a "Fix incorrect match" option, then that was the only way to really tell.

Unlike Google Music, Amazon Cloud Player offers a very thorough rundown of why specific files weren't matched or why they weren't uploaded. You can also head to the browser-based library and right-click on specific files to check and see if the "Fix Incorrect Match" option crops up.

iTunes Match was particularly picky about what it uploaded or matched to the cloud. Only two-thirds of The Weeknd’s Trilogy—not purchased from iTunes—was marked as matched, while the rest of the songs were tagged as having been uploaded. It was confusing. Why didn't the whole album match when all of the music files were the same bit rate and came from the same source? A quick search around the Apple forums revealed this is still a common complaint about Apple’s cloud music service.

Google Music could only match some of the more recent music we uploaded—essentially, tracks that were available for purchase in the Google Play store. Songs like "The Meeting of a Hundred Yang" by BT were matched in both iTunes and Google Music, but other albums, like those from indie band St. Lucia, were only uploaded to the cloud.

Amazon Cloud Player, on the other hand, did a fine job uploading tracks. Halfway through the upload process, about 3,302 tracks out of 3,419 were successfully matched. However, any song that did not have the precise metadata was either not matched or uploaded regardless if there was another copy that already existed in the cloud. Google Music also had this issue with metadata, often placing the wrong album cover on particular songs despite how they were set on the hard drive. (The service does offer a way to replace the album covers however, so you'll have to do so manually.)

One of the other major issues plaguing all three services is that they can run you square into your ISP's monthly bandwidth cap. If it can match your library, Google Music is usually much quicker about scanning and matching songs than iTunes Match and Amazon MP3. It even offers different bandwidth options for users, allowing them to choose whether they want to give the Music Manager bandwidth priority or allot the Manager barely any bandwidth at all. For users with gargantuan music libraries, expect to wait a while as both music services attempt to either upload or match those songs in the cloud. Amazon MP3 was the slowest uploader—it took about 12 hours to upload and match 4,001 music tracks.

Each service also features a limit to how many computers can be linked with an account. Fortunately for multi-device households, iTunes Match allows up to 10 devices to link with the service, while Amazon Cloud Player allows 8. Google Music also allows up to 10 computers to link with the Music Manager, though doing so produced duplicate library entries: Google's service uploaded the same album available on two different computers twice without cross referencing to check and see if it was already available. This is not only a little frustrating for the picky music archivist, but it’s also unfair to have those duplicates count toward the 20,000 song limit. iTunes fared much better with this because of the native “search for duplicates” feature available with iTunes, and it doesn't throw anything up in the cloud it has already matched. Amazon Cloud Player suffered greatly from its aforementioned metadata problem, producing too many duplicates across the board.