They describe what a thing or event looks like, and tell more about the condition of the thing or event. Program music is an example of nonliteral descriptive sound. Expressive nonliteral sound evokes a specific feeling, or mood. A musical fugue or sonata is an example of expressive non literal sound. Predictive sound signals a future happening.
Selective sound works on the figure-ground principle.
Sound perspective means that the video vectors and the audio vectors should correspond in their respective magnitudes. Zettl offers matching criteria to heed when choosing sound for a pre-existing video sequence. Historical-geographical matching means that the sound matches the pictures historically of geographically. Structural matching means that the pictures and sound are matched according to their internal structure - their dominant vector fields. It can be either one, two, or three-dimensional with varying duration.