Having just bought the score of HIMMELS-TÜR, I was wondering if someone who is familiar with it might be able to explain something about it for me. I understand that the score is notated in sections of 1 second per section, and that each of those sections shows the six levels (height-wise) of the door and where to strike the door in terms of those six levels. There is a dotted line down the middle of this, which looks like it is indicating the two leaves of the door, but the placement of the 'notes' or dots within these spaces (that is, on either the left or the right of the dotted line) then doesn't make sense - it certainly doesn't accord with how Stuart Gerber performs it on the YouTube video and also it would mean, if that's what the dotted line indicates, then always every second would begin on the left leaf of the door and move to the right, which doesn't happen and nor would you expect it to. IT also would make some of the glissandi or trills that spread over a few seconds pretty well impossible to play. So I assume the dotted line only indicates a midway point within the time frame of a second. So that leaves me with the question: how does the percussionist decide whether to hit the left or the right panel of the particular vertical level indicated in the score?
Perhaps you have read Richard Toop's excellent analysis of the score, in Perspectives of New Music vol. 50 (2012): 425–75. If not, I recommend it. The dotted bar-lines do not represent the left and right divisions of the door, but rather the halfway points within each one-second timespan. It is up to the performer to decide which side of the door to use, so the horizontal dimension is reserved exclusively to represent time.
I feel that it could be useful to have a discussion-forum on the music of Stockhausen. There are so many people from all over the world, young and old, learned and eager to get into contact with this musical world: musicologists, composers, musicians, music lovers; people who plan concerts - who write books or have to give lectures and so on. So there should be much stuff, many ideas that we can share. And when we have open questions, there may be people who studied just that and could give a hint or a stimulus.
A problem might be the English language, but i feel that is the only possibility that many people who are interested can participate. And we can exercise tolerance to mistakes!