This book is based on the Ph.D. dissertation, "Aesthetical and Technical Analysis of Selected Flute Works by Sofia Gubaidulina", by Zehra Ezgi Kara which was defended in March 2019. In this book, the music policies of the Soviet Union, Soviet avant-garde music and the works of Sofia Gubaidulina (1931-) are examined. The purpose of this book is to analyze selected flute works of Gubaidulina from a technical and aesthetic point of view and to explain how she uses timbral features, Fibonacci numbers, and symbolism in her works. In addition, since the analysis of the works of Garden of Joy and Sorrow (1980) and Quartet for Four Flutes (1977) provides detailed information of their content and structural features, this study constitutes a source for musicologists and performers.