How is the music store related to Ubuntu One?
An Ubuntu One account is required to purchase songs from the Ubuntu One Music Store. Ubuntu One accounts are free and come with 2 GB of personal cloud storage. Purchased songs are automatically transferred to your cloud storage, synchronized to all of your computers, and added to Rhythmbox. Customers will find a new library that contains purchases from the Ubuntu One Music Store. You can also fetch your music from your personal cloud storage through a web browser, just like all your other files.
Integrating the Ubuntu One Music Store with Ubuntu One gives consumers the security of online backup as well as convenience of auto-synchronization.
Please note that Ubuntu One synchronization does not support users who connect to the Internet through a proxy server. These users will need to download their purchases from the Ubuntu One website and manually add songs to their Rhythmbox library.