Help on Windows Movie Maker and Overlapping?

Well, I want to play a background track [music track] while my narrative plays as well. I've tried dragging the music track onto the my narrative, this works, but the problem is that as my narration starts, my music track starts to ascend and drown out my voice on the narrative as the video plays. How do I make is so that my music track and narrative play at the same time and no drowning out occurs. If anything, I'd like to make the music track a bit lower than the narrative but so that it can still be heard?