XBox Music Comes to Android
The service is Microsoft's Subscription based, and you can stream as much music as you want, all you need to do is purchase Xbox Music pass that will enable you to purchase the service.
You also can get a 30 Day Free trial, and if you wish to continue there is an offer for $9.99 monthly and $99.99 annual subscriptions. If you already have an subscription you just need to log in and start streaming music you want.
Although the app at the moment does not support the feature of offline playback, but the company has promised that the feature would be made available in the coming updates that are to be rolled out.
Also the service is only in some countries now, and if the app does not show up in your Phone's play store, assume the service is not available in your country.