The formula for getting that No. 1 hit album has gone through a lot of transitions.
While the movie breaks box office records, its soundtrack debuted at number-one on the Billboard charts.
Whether a song becomes a hit will depend where people listen.
On the day digital billboards spread news of the Boston Marathon bombing among Boston drivers, a judge's decision turned off digital billboards in Los Angeles. Cities and advertising companies argue over the bright billboards' value.