Canonical, the company behind the Ubuntu Linux distribution, has announced the official launch of the Ubuntu One music store. Integrated into the Rhythmbox music player in the upcoming Ubuntu 10.04 release, the store allows users to purchase downloadable songs and albums.

The music store is powered by 7digital, an online music distributor that offers over 4 million songs in the MP3 format without DRM. Canonical partnered with 7digital and developed the software that allows the music store to integrate with Rythmbox and Ubuntu One, the cloud service that Canonical launched last year.

The Ubuntu One music store is accessible through the navigation sidebar in Rhythmbox. When the user clicks on the Ubuntu One item in the sidebar, it will load the store interface in the main area of the Rhythmbox window. The store is basically a webpage that is loaded into an embedded WebKit frame. It's not fully integrated into the Rhythmbox track selection user interface like the Jamendo and Magnutune stores. The WebKit approach feels a bit less seamless, but it's arguably better because it allows a richer presentation. The music store interface shows a lot of album art and other visual elements.

The main screen of the music store will show a selection of popular and recommended songs. The user can click various elements to browse by genre or view recently added tracks. It also has a built-in search textbox which allows the user to find a specific artist, album, or track. When you select a specific musician or music group, you will see a concise description of the group along with a list of available albums organized in a grid with titles and cover images.

When you click on an album, you will see a list of available tracks with prices and download buttons. You can purchase songs individually or buy an entire album. Each song also has a preview button which you can click to hear part of a song before you buy it. The preview function will stream the first 60 seconds of the track and play it directly in Rhythmbox.

Users have several payment options, including credit card and PayPal. 7digital handles the transaction and can also store your credit card data if you desire.

The music selection is reasonably decent but isn't nearly as broad as the likes of iTunes and Amazon. The store's available music is said to vary between different geographical regions. 7digital has separate stores for the UK, the United States, Germany, the rest of Europe, and other parts of the world. I tested the US store.

It has most of the mainstream stuff that the average consumer will want, but it didn't fare as well when I started looking for more obscure items. The J-pop selection is especially weak, lacking some names like High and Mighty Color and Kajiura Yuki. Despite the gaps, there are some areas where the breadth of the selection managed to impress me. For example, I was pleasantly surprised to find that the store has a comprehensive assortment of Blind Guardian albums.

The music store is integrated with the Ubuntu One service in several ways. When a user purchases music from the store, the files are downloaded directly into the user's Ubuntu One cloud storage area. This means that the files will be propagated to all of the computers that the user has connected to Ubuntu One. The purchased tracks show up in a special section of the user's Rhythmbox music library, but are treated just like any other music file on the user's computer.

The files are also available from the Ubuntu One Web interface, which allows users to download individual files on any computer via a Web browser. The cloud storage integration is a great concept and is executed well. The downside is that the files purchased from the store count against your total Ubuntu One file sync capacity, which means that the free 2GB tier of Ubuntu One service will likely be insufficient for users who intend to sync a lot of purchased music.

You can, of course, move the files out of the synchronized storage area and put them anywhere on your filesystem if you don't want them to use your Ubuntu One space. The files don't show up in the regular Ubuntu One folder on your filesystem, but you can find them in the ~/.ubuntuone/Purchased from Ubuntu One directory.

The music that is sold through the store is encoded in the MP3 format. Although most users favor MP3 encoding because it is widely supported by third-party devices and software, it is somewhat controversial among certain Linux users who favor unencumbered formats such as Ogg Vorbis. The store does not offer Vorbis-encoded music and isn't likely to do so in the near future.

Ubuntu itself doesn't natively support MP3 playback in the default installation. Users have to install an additional package in order to get a licensed MP3 codec for GNOME's GStreamer multimedia framework. When the user first attempts to access the Ubuntu One music store, they will be prompted to click a button to automatically install MP3 playback support.

After downloading a few tracks myself, my overall impression is positive. Canonical has largely succeeded in making the music store feel like a convenient and well-integrated part of the Ubuntu user experience. Although it's impressive, the software is still in the beta stage of development and isn't entirely stable yet. It functions properly, but I experienced several crashes during my tests, primarily during the checkout stage of the purchasing process. There are also some minor bugs in the HTML user interface, like links that accidentally cause it to load the regular 7digital Web site instead of the one that is customized for Rhythmbox.

With additional refinement, the music store could be a win for Canonical and Ubuntu users. It's unclear exactly what kind of revenue-sharing deal the company has with 7digital, but there is definitely some kind of arrangement that allows Canonical to profit from the music sales. If the service gains traction among Ubuntu users, it could help boost Ubuntu's financial sustainability.