Sgt. Pepper's Lonely Hearts Club Band turns 50 next week — so what's been done to celebrate one of the greatest records ever? They've remixed the entire album! The word "remix," in fact, may not capture the scope of the project — it's more like someone rebuilt a pyramid with fresh bricks. But a question remains: Why would anyone do so? I traveled to New York to meet Giles Martin, who spearheaded the project, to find that out.