The joint venture, known as Napstertones, will provide ringtones formed from popular songs, artist voice shoutouts and wallpapers featuring the Napster Kitty and other graphics.

The service is immediately available to Cingular and T-Mobile subscribers, which is expected to extend the company’s reach into the US.

After the initial launch, Dwango and Napster hope that consumers of most major carriers will be able to access the Napstertones service during the summer. They are also planning to introduce it in Canada to Rogers Wireless and Fido this June.

As consumers in North America increasingly embrace personalized content on their mobile devices, digital music providers such as Napster are perfectly positioned to offer compelling content to wireless subscribers, said Alexander Conrad, president, Dwango Wireless.

In addition, Napster said it would debut a Napstertones prepaid card by the end of the summer.