Depending on the genre, it's easy to make a sequel from a successful first entry. All you have to do for an action movie, for example, is do exactly what made the first one so fun and make the action bigger, louder and more explosive. It's a formula that has worked hundreds of times for action movies, from "Rambo" to "The Avengers," but it hasn't always translated well to other genres. While "Pitch Perfect" was indeed a surprisingly fun, funny, toe tapping good time, how do you take a cappella to the next level?