Korean composer Isang Yun (1917-1995) was one of the few successful Asian avant-garde composers to blend philosophical elements from East Asia with Western techniques such as the twelve-tone method, Hauptton, Hauptklang, and Umspielung. In addition to the integration of Western and Eastern influences, a significant feature of Yun´s compositional language, found throughout his oeuvre, is the application of East Asian philosophical tenets into his works. The purpose of this dissertation is to develop a greater understanding of Isang Yun's life and music, more specifically the Quartett für Horn, Trompete, Posaune und Klavier. The dissertation is divided into five chapters. The first chapter of the dissertation presents introductory data, including the purpose and significance of the study. The second chapter provides pertinent biographical facts about Isang Yun and his works, obtained through research of authoritative books, journal articles, and interviews. The third chapter offers references to traditional Korean brass instruments in terms of their historical background, structure, and timbre. In addition, it also focuses on the processes by which Yun incorporated the compositional techniques of Hauptton, Hauptklang, and Umspielung to the work and their relation to Tao philosophy. The fourth chapter consists of an analytical and stylistic study of the Quartett; Yun's compositional language and formal structure are examined based on a stylistic assessment of selected examples from the work. The fifth and last chapter is a conclusion.