Statement of the problem. The article examines mode organization in the polyphonic cycle “34 Preludes and Fugues” by Ukrainian composer Valentin Bibik. The scientific novelty. The article explores modality and tonality as modeorganazing constituents in the polyphonic piano piece “34 Preludes and Fugues” by V. Bibik. The aim of the article is to indicate mode organization on the example of tonality and modality in polyphonic development of “The Third Notebook” (from the cycle “34 Preludes and Fugues”) by V. Bibik. The research methodology consists of integrated approaches to polyphonic music of the 20th century, including comparative and system-structural analyzes of musical works. Analysis of recent publications. The theoretical basis of the article is the latest publications by T. Bershadskaya (2008), N. Gulyanitskaya (1984), Yu. Kholopov (1972), M. Heinemann (2001), F. Hentschel (2006), I. Pustijanac (2016) and others. These studies investigate the compositional techniques of the twentieth century and their individual implementation into polyphonic works. When studying scientific sources, attention is focused on the interaction of polyphony and harmony since V. Bibik’s polyphonic cycle was chosen as the research material, in which polyphonic and harmonic patterns are closely intertwined, however, modal principles become the connecting factors, which is proved in the work. The presentation of the main material. The article investigates modern trends in the development of polyphonic music of the XX–XXI centuries, as well as the composer’s intention to create a mode organization in the cycle “34 Preludes and Fugues”. The article defines commonly used terms from the modern theory of musical modes regarding such phenomena as modality, tonality and their interconnection. The work presents the historiography of V. Bibik’s creative heritage in the context of the poliphony development. The work highlights the interaction of tonal and modal patterns in “The Third Notebook” (from the cycle “34 Preludes and Fugues”) by V. Bibik. Conclusions. The article argues the dominance of modality in structural organization of the cycle “34 Preludes and Fugues”. It is noted that the cycle accumulates a huge number of composer’s ideas regarding the interpretation of modern musical modes and tonal system. V. Bibik is not recognized as the author of the theoretical concepts of the mode organization in music, but the cycle itself is considered as a kind of composer’s creative manifesto, a vivid reflection of his conception of musical modes.