The article explores the life and work of Slovak composer Ilja Zeljenka (1932–2007) in the context of the socio-political situation in Czechoslovakia in the second half of the 20th century. His work exemplifies the fusion of avant-garde, modernist, and postmodernist aesthetics and illustrates the picture developmental pattern of Slovak music over fifty years. The composer searched for his own style for a long time, turning to serialism, aleatorics, sonoristics and electronic music, composing works in the spirit of the classics of the 20th century. He was the first to write a Slovak serial composition (Second piano Quintet, 1958), sonoristic and aleatoric pieces (“Oświęcim,” 1959), as well as an electroacoustic work (music for the film “65 000 000,” 1962). His 1961 Symphony No. 2 composed in the style of Prokofiev aroused discussion on imitation and originality. At the beginning of his career, Zeljenka had opposed the use of folk music motifs in contemporary compositions, but he later reconsidered this stance and his most performed pieces became those utilizing traditional folk sources. Employing the original elements called “ludism” and “cell” (“microserie”), Zeljenka ultimately created his own signature style.