A characteristic feature of Tadeusz Z. Kassern’s artistic output is a variety of musical styles, among which there is Post Romanticism, Post Impressionism, Folklorism, Expressionism, and different neoclassical sub-styles such as the Neoclassicism proper, Neoclassicism with archaic elements, Neoclassicism with archaic and romantic elements, as well as radical Neoclassicism. Among the abovementioned styles, the proper Neoclassicism is predominant. It is represented by Concerto for string orchestra, Concertino for oboe and string orchestra, the opera Comedy of the Dumb Wife to the composer’s own libretto based on a play by Anatole France, and many other works. The works belonging to this group are part of a widespread musical dialect, at the same time bearing traces of the composer’s individual choices that create a distinct musical idiom. This idiom, like the majority of idioms within the sub-dialect, is well-grounded in neotonal syntactic rules and formal strategies directed mainly at typical baroque and classical forms. Within the scope of the patterns replicated, it is close to the French and Polish proper Neoclassicisms. With the French Neoclassicism, it has in common static tonality, form, solutions in orchestration, as well as the use of quotations and parody; with the Polish style, it shares principles of symmetry and references to Polish musical tradition. As characteristic determinants of Kassern’s idiom, one can assume the simplest kinds of poly-tonality, considerable use of ostinatos, varied rhythmic unfolding, and multi-layered texture, which in its most developed form can be found in the expressionistic opera The Anointed.