When certain segments of the electronic work are compared to the string playing in Helikopter-Streichquartett, it is possible to imagine that the Arditti Quartet might well have been more comfortable in their task and employed a greater range of expression had they imitated the electronic sounds of Kontakte by way of preparation. Let's start with perhaps the most talked-about segment in Kontakte, Structure X at 17'05. I am reminded of those decelerating tones when I hear the cello's gradually accelerating first entry in Helikopter-Streichquartett, and if I am not mistaken the initially abrasive attack of the cello is very quickly 'rounded off' by the composer at his ProTools monitor to give the repetition a cleaner sound. Returning to Kontakte, Structure X continues with a series of sustained low pulsating tones, broken occasionally by rasping and metallic textures. These are the most powerful tones in the entire piece.
Frictional tremolo sounds occur only from time to time.
I have already mentioned the 'layers peeling off' at XI, which is analogous in terms of the idea of multiple sources coming together and moving apart against a constant background drone of impulses. There the suggestion of string tone is more marked. Stockhausen has acknowledged this could be the case. Certainly there is a much stronger emotional pull to the music at this stage, a powerful sense of brooding melancholy, of loss, of weeping. Note that he doesn't say exactly where the new material begins, which is passing strange for a person of such a meticulous disposition.