Three elements make up your soundtrack: voice over, sound design, and music. They can commingle in harmony, or they can wage full-scale war on each other—the casualty being the main message of your ad. To keep your soundtrack from turning into a warzone, follow the golden "triangle rule."
Soundtracks can get complex quickly, especially with wall-to-wall copy, dense sound design and a music track for emotional cue. The best way to make sure your ad isn't headed for disaster is to know each element’s role and priority before deciding the balance between them. If you know before audio post-production begins, you're at a greater advantage because you can actually build the supportive elements around the focal point. A good way to picture the balance between the three elements is to think of the soundtrack as a triangle. Then think about each of the three elements as a corner of that triangle. The top point being the loudest focal point and the other points underneath being supportive. At times the supportive elements can become the main focal point, as the main focal point takes a breather. In some cases the focal point is split between two elements, in which case, the triangle titters back and forth on one supportive corner. That one corner remains as a foundation, as the other elements dialog back and forth.
Look at the below figure to illustrate the point.
To keep your three soundtrack elements in harmony, there must always be at least one supportive element that acts as a foundation for the other focal points. The savvy media producer will know which of the three soundtrack elements (voice over, sound design, or music) will be carrying more weight—saving the production from soundtrack WWIII.