Google Music is a cloud storage service with a streaming music interface.

Screenshot by HowStuffWorks.com

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Back in the day -- and we're talking way back -- to listen to music you had very few choices. It really just boiled down to two: Find someone who could sing or play music or learn to do so yourself. Skip ahead a few centuries to the invention of the radio. With car radios and portable transistor radios, you had access to music on the go without having to hire your own personal musician. But your choices weren't unlimited -- you had to listen to whatever the radio station was playing.

A few decades later, magnetic storage was the way to go. You could get a cassette tape and listen to music on a portable player. But storage space per cassette was limited and the magnetic storage would degrade over time. Optical storage solved some problems, but you still had limits to the amount of music you could cram onto a single compact disc, and carrying around a portable player wasn't always easy. And if your CD player moved around too much, the laser inside it could skip bits of the music tracks.

The next big jump came when MP3 players entered into the mix. Now you could create a digital library of music and sync it to a portable device that could potentially hold hundreds of hours of songs. Players with large hard drive space could hold so much music that the battery would run out before you could listen to them all. But even this space had limitations, and porting music from one device to another wasn't always easy.

Now, we have cloud music services that promise to give us unprecedented access to music. Many of them have interfaces that allow you to access music across a wide variety of devices, including computers, MP3 players, smartphones, set-top boxes and video game consoles. You can create an enormous music library and enjoy it in more places than ever before. These are cloud services -- they utilize computer servers connected to the Internet to let you access information.

But what makes music cloud services tick and what are the limitations?