This dissertation investigates the aesthetic, cultural, and scientific context that allowed for the flourishing exchanges among the arts at the European fin de siècle. In contrast to standard impressionistic accounts of the Inter-Arts, it foregrounds and examines the time's immensely popular synaesthetic metaphor, while culturally and formally analyzing interartistic works. This work surveys the diverse and heterogeneous discourses that engage with synaesthesia: the figurative mixing or conflation of sense-impressions, for instance, in the perception of sound as color. It shows that the synaesthetic metaphor, usually treated as a trite Modernist mannerism, not only epitomized the synthetic aspirations of the Modernist arts, but also invigorated the exchanges among the arts at the fin de siècle by bridging aesthetic, scientific, and ethical discourses. As a nexus of controversial and fascinating cultural debates, synaesthesia acquired an intricate depth and complex resonance, which this dissertation examines by identifying synaesthetically informed fin-de-siècle cultural and scientific concepts (such as electricity and the phonograph) and using them as interpretative tools to analyze three specific interartistic sites of literary, artistic, and musical modernism. Chapter One shows how Oscar Wilde's Salomé overcomes its own language by turning to the senses, generates new extra-verbal life, both sensory and interartistic, and is transposed across the senses and the arts in Aubrey Beardsley's drawings and Richard Strauss's opera. In the second chapter, this work examines Aleksandr Skriabin's synaesthetic symphony "Prometheus" and the Russian Symbolist poetics of mystical and electric light. The final chapter discusses the phenomenological synaesthetics of Rainer Maria Rilke's middle-period thing poems (Dinggedichte) and their involvement with the visual arts, by focusing on Rilke's fascination with Rodin. It then studies the development of Rilke's synaesthetic theory in his late "Sonnets to Orpheus." Figured as a synaesthetic and phono-graphic translation, Rilke's poetic act seeks both a primordial and a technologically motivated wholeness of sensory experience. Additionally, this work offers an online companion to the dissertation that makes all the musical examples playable: an important feature of the dissertation is its combining of musicological and literary analysis, as well as visual analysis. "Beautiful Colored, Musical Things" proposes a new way of conceptualizing early interartistic Modernism, by suggesting that the synaesthetic metaphor defines and motivates the interartistic exchanges at the fin de siècle. In its critical and methodological goals, this dissertation seeks to foster interdisciplinary exchange, and to overcome the limitations of discipline-bound criticism.