Napster and XM Satellite Radio unveiled a beta version of <A HREF="http://news.zdnet.com/2100-9588_22-5964618.html?tag=zdnn.alert">a joint music offering.</A> The new service is designed to let satellite radio subscribers access, purchase and download broadcasts on about 70 music channels available over XM, the companies said. In addition, users can access Napster's music catalog and buy tracks from it. The XM + Napster service is available at a new Web site, to be marketed by both companies.