The Synesthetic Vision

Kandinsky described a crossing of the senses, often called synesthesia, that let him hear colors and see sounds. Yellow rang out like a trumpet; blue sounded to him like a cello; red pounded like a drum. He insisted these were real sensations and not just metaphors, and they shaped his whole theory of art — though scholars still debate whether he had true neurological synesthesia or was describing his color-sound links more poetically.

From them he built a system matching colors to emotions and sounds. Warm colors seemed to advance; cool colors to recede. Sharp angles created tension; curves brought calm. He set this all out in his book Concerning the Spiritual in Art.