Thank you very much everybody for your effort; I also have seen only bits of it, but maybe there is a specialist who knows more about it? Originally, I posted this question to the 'Serious Discussion'-forum... don't know why it has been removed...
There is no official video recording as far as we know but there is a silent amateur video which was used for various documentaries. As far as I know the video is only about 6 minutes but the actual performance was not much longer, anyway.
It's a general knowledge question, therefore the topic was moved to the General Forum - which is not a trash forum, although there are a couple of trash topics :)