Starting December 1, 2014, the free Xbox Music streaming feature will be discontinued. After that, you'll be required to have Xbox Music Pass (a subscription service for $9.99/month) if you want to be able to created playlists and stream music across PC, tablet, Xbox, your phone and the web.
If you've purchased any music through the service, those songs won't be affected. Also, your playlists, radio stations and collections that you've created will continue to exist, but it'll require an Xbox Music Pass to access them.
Microsoft does offer a 30-day trial for Xbox Music Pass, so you could always try it out and see if you want to continue paying for the service.
