This thesis presents orthographic analyses of selected works of Musorgsky. The thesis argues that more traditional methods, such as voice-leading analysis or set-theory analysis, are, because of their particular historical and stylistic origins, limited in their application to Musorgsky's music and, on this basis, it sets out to demonstrate the value of an orthographic approach. The thesis takes existing orthographic analyses of the music of later transitional, or post-tonal, figures such as Skriabin and Bartók, and extends the application of this approach to an earlier transitional notation and attempts by composers to give cogent articulation to an increasing number of non-traditional pitch structures. The thesis falls into six chapters. The first chapter reviews common perceptions of Musorgsky, especially the notion that his music is somehow technically deficient or limited by a self-didactic eccentricity. It concludes by surveying analytical approaches to Musorgsky's music, and orthographic analyses of Bartók and Skriabin. The second chapter expounds the methodological principles of orthographic analysis. It examines common-practice conventions of orthography and then takes typical orthographic "problems" found in post-common-practice styles in order to show how novel structures are illuminated by the notational friction described above. The chapter concludes with a case study of Brahms's Intermezzo op.118, no 6, which demonstrates how conventions of common-practice notation are sustained in a piece from the central tradition. Chapters Three and Five are dedicated to the analysis of Musorgsky's music. Each takes a work, or selections from a work, leading to a discussion of several related orthographic and tonal issues. The music examined includes selected passages from Boris Godunov and Pictures at an Exhibition, and the entire song cycle Sunless. Several issues arise from these analyses, notably Musorgsky's use of octave symmetry and polymodalism, and his radical conception of relationships between individual chords and prevailing keys. The sixth chapter synthesises these findings and presents a revised view of Musorgsky's tonal thinking and practice, based on his orthography. At the centre of these findings lie key observations concerning the fusion in his music of "functional" and "non-functional" elements. This concluding chapter also speculates on the further potential role of orthographic analytical methods for musics of a traditional nature, especially those of Eastern European traditions.