Radio Adverts

One of my secondary tasks is to create a radio advert for the film that I make. I find the concept of adverting a film on the radio quite strange as it seems like commercial suicide. Why would you as a radio station, promote the thing (film) that is killing your business? Anyway, they are quite hard to find because no one really records adverts about film, as they tend to be short, sweet and straight to the point. They state the director, the main actors, the reviews it has and finally the name of the film. The only ad I could find for a film was that of a Jimi Hendrix film from 1973. It basically features a clip of a concert, before the radio announcer tells you what the film is. If anything this shows me how not to do it because it is long and dull, with a sudden start and a poor ending.