In the article the role of this source in the understanding of the life and work of the Ukrainian composer is considered. Due to this source’s involvement in the scientific discussion, the process of biographical reconstruction of various stages of the life and creativity of B. Lyatoshynsky was elaborated. The informational richness of this source helped to illuminate and clarify a number of gaps and clarifications in the artist’s biography, the influence of the Polish component on the formation of his creative personality, especially of the early and late periods of his life. The genre classification of the source is a literary portrait, a fairly common form of modern memoirs. Written several months after the composer’s death, Strashynsky’s memories, in fact, became the first account for the general public of the life narrative of B. Lyatoshynsky. Written for the Polish art magazine «Ruch Muzyczny», the memoirs of O. Strashynsky became the first posthumous representation of B. Lyatoshynsky’s creative interests for the Polish artistic community, which, to some extent, was aware of the «Polish part» of the late-stage work of Lyatoshynsky. After all, the composer was relatively often heard in Polish concert halls and on Polish radio and television. These memoirs became one of the first attempts to include B. Lyatoshynsky in the Polish-Ukrainian (at that time — Polish-Soviet) artistic dialogue. Realized through the genre of literary portraiture, this dialogue of cultures, according to O. Strashynsky, was associated with the formation of B. Lyatoshynsky as an artist in the Polish environment and the constant transformation of Polish discourse throughout his whole creative life. Constant exploration of his Polish (ancestral) and native Ukrainian cultures, especially in the late period of his creativity, on the principle of convergence (synthesis) of many Slavic cultures, resulted in the so-called Pan-Slavic subject of the late stage of the Ukrainian artist’s work.