If you've got a big digital music collection, you may want to consider signing up for a digital music storage locker.
Some of the biggest players in mobile music -- Apple, Amazon and Google -- are offering such services. For a small annual fee -- or none at all -- they allow you to keep a copy of your music collection stored on servers on the Internet.
For each of the services, the uploading process can be time-consuming. But once you go through it, the result is a secure backup of your music collection that you can access from any PC or Mac and from a mobile device anywhere you have an Internet connection.
I've been testing out all three of the new services. I liked all of them, but they each have their drawbacks. Your favorite will depend a lot on what devices you own.
As might be expected, Apple's iTunes Match is the best choice for owners of Apple handheld devices, including the iPhone. It costs about $25 a year and allows users to store up to 25,000 songs on Apple's servers.
"Store" isn't actually the right word, though, because iTunes Match, a new feature built into Apple's popular iTunes computer software, works a bit differently from other digital locker services.
Instead of requiring you to upload your entire music collection, iTunes uploads only those songs it can't find on Apple's servers. You get access to both matched songs and uploads; Apple doesn't make a distinction in its cloud.
The advantage of Match is that it requires far less bandwidth and time than uploading your entire collection. In my case, Apple was able to match all but about 500 of my 8,800 songs. The total process took about a day and a half, but it probably would have been much shorter on a computer more recent than my 6-year-old Mac.
iTunes Match allows you to stream music from Apple's servers or download albums, playlists or individual songs to your device. Depending on the speed of your connection, it can take a second or two for a song to start streaming. The sound quality was good.
One problem with iTunes Match is that it only works with newer iOS devices. So if you have an Android phone or even an iPhone 3G, you can't use the service.
It also has an annoying bug. When you turn on iTunes Match, one of the cool features in iOS devices -- the "genius" playlist of 20 tracks based on one particular song -- disappears.
Amazon's Cloud Player service is the best choice for owners of the new Kindle Fire tablet. But it's also a good option for owners of other Android devices. That's because for $20 a year, it allows you to store an unlimited number of songs.
Unlike iTunes Match, Cloud Player is part of a true storage locker -- you upload your entire music collection to it, except for those you've bought from Amazon, which are automatically placed in your locker.
One of the advantages of Amazon's service is that it's not tied to just Amazon's devices. You can also access the service through Amazon's MP3 app on other Android devices. And you can get to it on the iPad through its Web browser.
Like the iTunes Match service, Cloud Player allows users to stream or download their music from Amazon's servers through an app. You can stream but not download songs to a mobile device through its browser.
Uploading songs to Amazon took several days in my case, in part because the application used to upload songs to Amazon stalled out several times.
I had other problems with Amazon's Uploader. Unlike iTunes Match, it didn't copy over my iTunes playlists, meaning I'd have to manually reproduce them on Cloud Player. It also doesn't check to see if songs are already in your library; I ended up with duplicate copies of some of my songs because I had already uploaded some of them from my work computer. And unless you buy songs from Amazon, it doesn't automatically add new tracks to your library in the cloud.
The Cloud Player website has its own shortcomings, most notably that it's basically unusable on the iPhone.
Google Music is my favorite all-around service because it's free and works well on the widest range of devices. Owners of standard Android smartphones and tablets can get access to Google Music through Google's Music app, which comes with many of those gadgets. Owners of other touch-screen devices, such as the iPhone or the Kindle Fire, can access Google Music through a Web app that was designed specifically for them.
As with Amazon's Cloud Drive, you have to download and install a separate application on your computer to upload your songs to Google Music. I had even more problems with Google's Music Manager than I did with Amazon's Uploader. It stopped working repeatedly while uploading my files, requiring me to shut it down and restart it. Thanks to all that starting and stopping, it took even more time to upload my collection than did the Amazon program.
I also ran into the problem of duplicate files. When I ran the Music Manager on my computer at work, it didn't recognize that some of the songs I was uploading were copies of the same songs I'd already sent to Google Music from home.
Music Manager does have some big advantages over Amazon's Uploader. After you use it, it will run in the background and automatically upload any songs you add to your computer. So you don't have to do a manual scan ever again. And it also recognizes and uploads your iTunes playlists, so you don't have to duplicate them.
Once you have your music in the cloud, Google Music works great. Android users can see and play their entire collection and easily save individual songs, albums or playlists for offline listening. Via the Web app, users of other devices can play songs even while using other apps.
But Google Music has one big shortcoming compared with other services: Once you've uploaded your songs to Google, you can't download those tracks back to your computer. That could be a problem if your hard drive crashes and you want to use a different service.
Still, it's hard not to like a free service that lets you listen to your music just about everywhere.