"You know, and it really doesn't have a lot to do with the movie. That's the trick to doing a good musical is that, if you take that music number out, there's less to the movie there. You would miss it"

Trey Parker is suggesting that a great musical should have music numbers that are important to the film. If you secure the music numbers, there would be less to the motion picture. He is stressing the significance of music in a musical, as it is a key element that makes the movie pleasurable and memorable. He is likewise recommending that the music needs to be well-integrated into the motion picture, so that it is not simply a random addition, however rather an essential part of the story. This quote highlights the value of music in a musical, and how it can make or break the movie.