The (Syn)Aesthetics of Modernism is an examination of interactions between music and the visual arts in the first quarter of the twentieth century. It aims to demonstrate how a synaesthetic view of the arts might countenance a fresh historical model and a more inclusive definition of musical modernism. The interdisciplinary relationships considered inspire a fundamental reassessment of the progression of European art music in the early 1900s. An appraisal of the manifold understandings of “modernism” precedes two substantial case studies. Schoenberg and Satie have been chosen for the contrast and positive comparisons they bring to the topic: Schoenberg is a composer whose place in the pantheon of musical modernism is assured, while Satie’s situation differs due to the lesser nature of his reputation and a radically different musical style. This study ultimately proposes a revised assessment and definition of modernism from an interdisciplinary perspective. The case studies reveal how the net result of the convergence of music and the visual arts was to be a divergence towards autonomy on the one hand and music at the service of art on the other.