An Xbox subscription is 9.99 a month. But that is for a streaming plan which you are not needing. Xbox can be turned off in the setting and music still plays. I think you are trying to search for music but instead are hitting the button meant to search music on Xbox. Playing your own music does not require a login. If I can't find your music try adding a playlist with songs that are on the SD card. Then play that playlist and ot should trigger the app to search for new music. Or just soft reset the phone and it should show up.