This article focuses on a passage from Marcel Proust’s La Prisonnière, in which the narrator, while performing the novel’s iconic Vinteuil Sonata on his piano at home, meditates on the imaginary origins of works by Jules Michelet, Richard Wagner, and Honoré de Balzac. While purely speculative, the narrator’s versions of these origins—largely improvisatory and subject to chance—highlight a musical undercurrent inherent even in the medium of literature. Taking up Deleuze and Guattari’s statement that Proust understood the whole of the work as yet another part, on par with the parts it seems to bring together, this essay explores the relationship between improvisation and composition in music, and how their complex interweaving can shed light on both the creation and the experience of art more broadly.