Synesthesia is a condition in which stimulation of one sense triggers sensation in another. While very few people have it, most of us are able to understand it at the level of analogy. Musicians, for example, use "chromatic" scales (derived from the Greek word for color), while visual artists routinely employ musical terminology such as tone and harmony.
A contemporary incarnation of this cross-fertilization of the senses is the 2005 Turner Prize shortlistee Jim Lambie. His latest solo show at Tokyo's Hara Museum of Contemporary Art, "Jim Lambie: Unknown Pleasures," openly flouts the division of the senses.
Lambie, who was once in a rock band called the Boy Hairdressers, which later went on to become the more well known Teenage Fanclub, finds it hard to separate the visual from the aural, as he revealed at a gallery tour last month at the opening of the exhibition.