Orchestration—and, with it, the roles that timbre plays in musical rhetoric, expressive trajectories, and the choices made by performers—deserves more attention from scholars than it has received. In an ongoing project, Blair Johnston is examining the rich ways that orchestrational choices in post-Romantic symphonic works interact with the “structures” described by more conventional music analysis, an area that features music-theoretic vocabularies that do not always allow for easy discussion of certain dimensions of sound—in broad terms, its shapes, its colors, its densities—that are especially essential in music from this era. This talk will explore this through the use of late symphonic works by Sibelius (excerpts from the Fifth, Sixth, and Seventh Symphonies and Tapiola), music in which complex approaches to musical form and material are fused to a highly individual orchestrational language—indeed, music in which there may be almost no line between form, material, and timbre.