Wassily Kandinsky (1866-1944) was a Russian painter who developed the first fully abstract visual art in the European tradition, and who did so because his synesthesia made him see no meaningful distinction between music and color. Kandinsky's form of synesthesia was chromesthetic: sound triggered color experience, music triggered visual experience, and the mapping was specific enough that he could describe individual musical instruments in terms of their characteristic colors. In his theoretical treatise On the Spiritual in Art (1912), Kandinsky wrote: "Yellow is the typical earthly colour… The sound of yellow is analogous to the shrill notes of a trumpet." "Blue is the typical heavenly colour… When it sinks almost to black, it echoes a grief that is hardly human." These are not metaphors in the literary sense. They are reports from inside a perceptual system in which the relation between color and sound is not an artistic choice but a fact of experience. Kandinsky has famously described attending a performance of Wagner's Lohengrin and seeing the music as specific colors appearing in front of him — an experience which he later identified as the moment he understood that representational painting was limiting him, because representational painting required him to depict objects when the actual content of his perceptual life was the direct cross-sensory relationship between music, color, and form.
Abstract art, in Kandinsky's case, was not an escape from representation. It was a more accurate representation of what his cognitive architecture was actually perceiving. The paintings were an attempt to produce on canvas the same synesthetic cross-modal event that a Wagner opera produced in him — a direct visual analog of musical and emotional content, without the interfering layer of depicted objects. His treatise describes at length how specific geometric shapes have specific emotional weights (triangles sharp and ascending, circles whole and contained, squares stable and earthbound), and this almost certainly reflects a shape-emotion form of synesthesia operating alongside the sound-color form. The integration community that received Kandinsky's work — the early twentieth-century avant-garde, the galleries that showed it, the critics who defended it, the theorists who placed it in art-historical context, and eventually the museums that preserved it — did the civilizational work of turning his idiosyncratic cross-sensory perception into a new artistic tradition that subsequent generations could inherit without having to be synesthetes themselves.