question: What is the last name of the person who continued to form acquaintanceships with other experimental and serialist composers ?
context: Despite a political climate that was unfavorable to modern art (often denounced as "formalist" by the communist authorities), post-war Polish composers enjoyed an unprecedented degree of compositional freedom following the establishment of the Warsaw Autumn festival in 1956. Górecki had won recognition among avant-garde composers for the experimental, dissonant and serialist works of his early career; he became visible on the international scene through such modernist works as Scontri, which was a success at the 1960 Warsaw Autumn, and his First Symphony, which was awarded a prize at the 1961 Paris Youth Bienniale. Throughout the 1960s, he continued to form acquaintanceships with other experimental and serialist composers such as Pierre Boulez and Karlheinz Stockhausen.
  During the 1970s, Górecki began to distance himself from the serialism and extreme dissonance of his earlier work, and his Third Symphony, like the preceding choral pieces Euntes ibant et flebant (Op. 32, 1972) and Amen (Op. 35, 1975), starkly rejects such techniques. The lack of harmonic variation in Górecki's Third Symphony, and its reliance on repetition, marked a stage in Górecki's progression towards the harmonic minimalism and the simplified textures of his more recent work. Because of the religious nature of many of his works during this period, critics and musicologists often align him with other modernist composers who began to explore radically simplified musical textures, tonality, and melody, and who also infused many of their works with religious significance. Like-minded composers, such as Arvo Pärt and John Tavener, are frequently grouped with Górecki under the term "holy minimalism," although none of the composers classified as such has admitted to common influences.
answers.text: Górecki