The article examines the changes occuring in chamber-instrumental music during the 20th century. The process of origination and further strengthening of the tendency of the composer to delegate decisions to the performer, which significantly changes the creative process and the final piece of music, has been outlined. This indicates elements of performativity, such as aleatorics, associated with unpredictability, and improvisation in the performance process. As part of the study of the mentioned topic, the evolution from atonality and dodecaphony to integral serialism and, as a reaction to total determinism, the emergence of aleatorics, which marked a significant renewal in compositional techniques and performance practices as a reaction to changes in sociocultural processes, were followed. Analyzing the works of composers John Cage, Pierre Boulez, and Karlheinz Stockhausen, as well as the their Ukrainian peers, the paper attempts to find the interrelations between the mentioned processes and the philosophical and aesthetic concepts of the mid-20th century. Thus, a change in the communicative mechanisms of interaction between the composer, the performer, and the listener with the redistribution of functions in the process of forming the final piece of music was presented.