Synesthesia: Tasting Colors, Seeing Sounds

In 1812, a German physician named Georg Tobias Ludwig Sachs published a medical dissertation on albinism. Buried inside it was the first clinical description of a strange and personal condition. Sachs detailed how both he and his sister experienced the world differently. For them, specific musical notes, numbers, and even days of the week consistently triggered colors. It was not an act of imagination; the links were automatic and felt as real as the physical world. For example, he described seeing the musical tone G as green and the note B as an ash-gray color. His account, written in Latin, remained largely unknown to the wider scientific community for decades. What was this phenomenon that connected two separate senses in the brain?