If you’re lucky, you may someday get a chance to watch a movie whose soundtrack isn’t yet finished. You’ll be scanning channels and stumble across a special about how movies are made, or you’ll see a tribute to a film composer, or you’ll rent a movie DVD that includes a “making of” documentary. These TV shows and DVDs sometimes include a couple of minutes of the finished movie as it looked before the musical soundtrack and sound effects were added.

At that moment, your understanding of the film medium will take an enormous leap forward. “Jeez,” you’ll say, “without music and sound effects, this $100 million Hollywood film has no more emotional impact than…my home movies!”