I have been struggling to sync music over to my Lumia 920 so I've used Windows Media Player to do it. However, neither Zune Pass or downloaded XBOX Music pass music will work. I know they both use different DRM but there isn't any software that will help me activate the device to work with either "Pass."
I tried a direct download on the phone but it said I am at my max number of devices. I am an old Zune Pass "Keep 10 Songs" user and from what I understand, I was grandfathered in on 3 PC's and 3 Devices. (correct me if I am wrong). I know the new "rule" is a combo of 4 devices.
You can manage XBox Music devices from the XBox website. Go to Xbox 360 - Official Site - Xbox.com, sign in using your Live ID, and then click on "My Account" under your login name. On the new page that comes up, select "Manage music devices" under the device management section, and you can see and remove older devices from your XBox Music pass list. They're probably limiting your account to 4 devices (not sure if you can get that adjusted due to the grandfathered account).
You can buy tracks on your phone using the MP3 credits on the phone. You can buy the track, and it will display that it will use one song credit. When you complete the transaction, it will show you how many song credits you have pending.