In particular In the second interval both A and B should be flatted in the third there is no G in the original tetrachord in the fourth and fifth there is no B natural in the original tetrachord in the sixth there is no A natural in the original tetrachord I m also not aware of Webern or Schoenberg using this tetrachord much explicitly There might be a few of them here or there in their music but I m pretty sure it s not a significant feature of either s music as it certainly is in Carter I don t know about Perle I don t think either Webern or Schoenberg even knew of the special properties of this tetrachord The literature on Webern and Schoenberg that I know certainly doesn t mention this Mind providing citations Finally the second External Link is dead It s also questionable Carter s Night Fantasies is usually cited as the quintessential example of registrally deployed all interval twelve tone series quite a different phenomenon than all interval tetrachords There might be all interval tetrachords within it though it d be nice to have the link fixed so we can see 146 96 130 201