EVEN if you haven't consciously registered it, the rapid change in styles of music programmes on television must be part of everybody's experience. Just a clip from Ken Russell's Elgar film is enough to make the point, as you plunge into a world that now seems a million miles away. In Germany, the phenomenon has now become a subject of a documentary in its own right. The first part is a retrospective, promising to start from the days of 'para-mediatic conceptions of content' (no doubt a picture or two will tell that like it is) and moving on to the age of the pop video. Intriguingly, the second part will let young graduates loose at the state-of-the-art end. If you happen to be in viewing distance of WDR Television on 12 August you'll catch it late.