AND would render the text formatting that you have within the XML files (text color, font size, swiping colors, etc.) AND on which we could apply a looping background (static or dynamic) - this will be an input from the rendering software.
This would be working like this:
mp3 = music file
xml = formatted lyrics synchronisation with music (including timing and lyrics)
looping background = input of the karaoke player that could be a static or dynamic image / video.
The player should be able to render these 3 files in real time.