No music on Windows Phone 8

I’ve loading a music file which is an xnb built from a wma file like this:

_music = Content.Load(“Music/Chipho_instrumental”);
MediaPlayer.Play(_music);
MediaPlayer.IsRepeating = true;
MediaPlayer.Volume = 0.5f;

The same xnb file works in my Windows 8 project.

In Windows Phone 8 there are no errors but there is no music. When I query MediaPlayer.PlayPosition the song position has progressed, so it thinks it’s playing.

What am I missing?

use mp3 instead of xnb