webern is a deeply European composer. and from this tradition and historical awareness he never even uproots himself, no matter how much he "undermines"... whatever that means to undermine. he is always within this river.
whereas feldman, I see him as being completely outside of this river.
so, all in all, it seems superficial to me to speak of parallels between webern and feldman based on technical issues like repetition, tempo, etc. etc. I don't think one can make a comparison and a parallelism between webern and feldman of the same type as can be made, for example, between brahms and mahler. brahms and mahler, unlike feldman and webern, live within the same river... they are almost one being the continuation of the other... father and son (the sense of family to me is one of the most characterizing elements of European culture in any field...), another example of comparison within the same river is that between mahler and webern.
but the level of kinship between feld [feldman] and webern is of a completely different nature. it is true that the two had some contact, feld had listened to webern's music (it is said that the meeting between feld and cage was precisely at a concert with music by webern... and the culprit was... eheheh), but the Americans found themselves having to start "from scratch", in great contrast to the Europeans... schonberg knew something about the burden of tradition hehehe, as xen recalls, composition courses last 10 years here, there is a reason for it, and it is precisely this long musical tradition, so precious but also quite cumbersome.
feldman was for a long time passionate about carpets, so much so that he became a collector. well, I find that the kinship to be sought between webern and feldman is more similar to this passion for carpets.
instead, I struggle to see the parallelism between scelsi and feldman. ok, there are repetitions but... even bach's passacaglia for organ is "repetitive"... it is also true that scelsi is a somewhat anti-academic and non-systematic composer... so he situates himself in a position a bit... let's say on the margins of the river, to continue the previous metaphor... but I don't know... "instinctively" I don't really perceive this parallelism...
and mea culpa, eh!