In multimeadiaproductions is an important role for sound in all possible ways. As for textual explication, sound can influence the interpretation of a picture.
examples:
A publicitymovie shows a car that is taking a heavy weight uphill. If you hear triomphantic and heroic music then we will interprete the scene completely different than we hear something like iiiiiiiiiiiiiii. For the popularity and sales of the car can this make a big difference.
A videoclip without sound looks like something stupid; many computergames without music looses his attraction; without music a film will not be a thriller.