This thesis examines the life and work of Russian composer, Sofia Gubaidulina (b. 1931) during the period up to 1986, after which, she was allowed to travel beyond the Soviet Union. The context of the environment in which she lived, the repressive secular state of the U.S.S.R., has been considered. The sources of inspiration in her music have been explored, in particular her religious belief and its expression in music. Throughout the project, numerous isolated and disparate writings about Gubaidulina have been brought together. The collection, presentation and summary of this data, and the evaluation and critical interpretation of the data, has resulted in a valuable collection of thoughts and observations concerning this renowned composer, including her own explanations. This body of work examines areas of the composer's life and work, the influences and principal musical interests which have shaped her compositional identity, and the importance of extra-musical interests and compositional processes. This work provides the background context for the detailed analytical study. The most substantial part of the research project is an in-depth analysis of Seven Words (1982), for cello, bayan and string ensemble, a piece of particular importance. Multifarious analytical methods have been used to illuminate the work. The evolution of the score, in its various forms, has been examined. Key observations include the identification of the characteristics of Gubaidulina's musical style within this work, an interpretation of the symbolic significance of the musical materials, and an investigation of Gubaidulina's use of Fibonacci numbers in the macro and micro levels of the work. A further important innovation is the use of original graphic representational techniques to display complex contrapuntal textures. This comprehensive analysis illustrates Gubaidulina's musical personality, and elucidates the technical craft of composition. From these observations, Gubaidulina's compositional aesthetics and procedures are revealed.