In this study, the music policies of the Soviet Union, Soviet avant-garde music and the works of Sofia Gubaidulina (1931-) are examined. The purpose of this study 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 work. 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 flute students, musicologists, and performers. In this study, the hypothesis is that the rigid policies of the Soviet government directly affected Gubaidulina’s music and philosophy of life by leading her to spiritualism and it can be observed in her flute works. In order to illuminate the effect of the regime’s restrictions and censorship in art – on Gubaidulina’s works in particular – the policies applied to music and musicians since the foundation of the Soviet Union are examined in detail in the first part of the study. In this part of the research, descriptive and historical research methods are used to examine the evolution of Soviet music and the effects of politics on music. Accordingly, the most accurate and reliable sources available have been referred to, and previous experiences have been examined. As a result of the research, it is seen that the historical processes in Soviet music directly affected Gubaidulina’s sense of composition and her oppositional stance. One of the most important reasons for Gubaidulina being one of the most prominent composers of our time is her ability to create a distinctive and unique style for the country and the time that she has been brought up in, and her ability to make skillful use of spiritual elements in her work. The third part of the study focuses on Gubaidulina’s works, her composing styles, and her experiences as a female composer living in the Soviet Union. Inspired by religious and mystical elements, literary works, and the composers she admired such as J. S. Bach and Webern, Gubaidulina often concentrates on a particular subject and depicts it in her works. Unlike the philosophy of abstract art, Gubaidulina believes that music must establish a connection between the divine and the earthly, and composes all of her works with religious feelings. For example, the fact that the instruments make glissandos in opposite directions in a crisscrossing manner is a method used by Gubaidulina to symbolize the Cross and the Crucifixion. Gubaidulina uses similar symbolism in many of her works, including the two flute works analyzed in this study. One other distinctive characteristics of Gubaidulina’s work is the use of elements that contain dichotomies (e.g. legato against staccato, or chromatic/microtonal against diatonic). As can be understood from the titles of her works including Light and Darkness (1976), Garden of Joy and Sorrow (1980); Vivente-Non-Vivente (1970, xx Living-Non-Living), in many of her works she symbolizes the connection between life and death, in other words, the divine and the earthly. The formal structures of Gubaidulina’s works are often related to numbers. Although she is known to use the Fibonacci numbers which symbolize the harmony of the universe, and some other numbers containing mystical meanings in her work, since the works examined in this study are among her early works, such formal structures have not been encountered. In the fourth chapter of the study, Allen Forte’s pitch class set theory is used to analyze Garden of Joy and Sorrow (1980) and Quartet for Four Flutes (1977). In the set theory, one octave is numbered by dividing it into twelve chromatic pitches, where the note C corresponds to zero. This definition does not differ for enharmonic sounds, meaning that it is represented as C/B#=0, C#/Db=1, D=2, and so on. The main purpose of using this method is the mathematical calculation of the pitch spacing. For example, the E-G# interval consists of 8-4=4 semitones. The plus (+) or minus (-) signs are used to indicate descending or ascending intervals in the melodic structures. Analyses showed that the general melodic line of Garden of Joy and Sorrow (1980) consists of ICs +1+4-1-4, and its inversions. Similar symmetrical interval sets (+1-1) are also found in Quartet for Four Flutes (1977). This shows that symmetrical structures are another important element of Gubaidulina’s musical aesthetic. Another method used in the analysis section is that of expression parameters (EP). This method was developed by Gubaidulina’s schoolmate, the musicologist Valentina Kholopova, and aims to explain the elements of dichotomy in her music. Kholopova divides the EPs into five groups in the form of (1) articulation and sound production methods, (2) melody, (3) rhythm, (4) texture, and (5) composition writing. Since each parameter is used as dissonance and consonance in itself, a method called Parameter Complex consisting of ten parameters has emerged. In this study, Kholopova’s method was applied to both flute works and presented in the form of tables. In analyzing the work of Garden of Joy and Sorrow (1980), the literary works that create inspiration, and the use of certain symbolism with proven accuracy, are also focused on. For example, in this work, Gubaidulina is inspired by a poem by Francisco Tanzer and a book by Oganov entitled Sayat Nova. Based on this, it is concluded that the work contains an east-west synthesis. In the light of the information she provided in some interviews, it is also concluded that the expression of Joy and Sorrow symbolizes the joy in the sky and the sorrow on the ground. Here, too, a reference can be made to the divine and the earthly. Quartet for Four Flutes (1977) has an abstract structure which is uncommon in Gubaidulina’s works. Thus, this work is analyzed by prioritizing the formal structure, the timbral qualities, and the use of advanced techniques. In this work, Gubaidulina’s idiosyncratic sonority conception usually involves the use of multiphonics, microtonality and chromaticism. In conclusion, the contributions of Gubaidulina to the flute field are revealed, and the findings related to the composition techniques, and aesthetics of her flute works are interpreted. This work is important in terms of creating resources for students, composers, performers, and musicologists who are interested in Soviet avant-garde music and, in particular, Sofia Gubaidulina.