The senses sometimes get mixed up so that people speak of “hearing colors.” The condition is known as “synesthesia.”
One case is that of a young girl who came from a very musical family, and gave a piano recital at the age of 11. She has a definite sensation of hearing colors. Of the various theories to account for this condition, one is that it is due to the color of the keys on the piano. In the young lady referred to there was a definite association of blackness with low tones, and of whiteness with high tones. Thus C2 is black and red, C4 is pink, G4 is real light blue, and C5 the lightest pink, almost without color.
Other reactions, however, are more complicated and cannot be explained on the basis of the association with piano playing. For instance, she associates musical instruments with colors. Tuning-fork tones are like rainbow colors, and when louder they become clearer, “like prism colors we have in our Christmas garden.” The flute is red; the violin is a dirty red; the clarinet is a pretty red; the French horn is a rather pretty red.
Other individuals with this condition who have been studied have even more peculiar reactions. One, for instance, described the lowest piano tones like toast soaked in hot water; the middle regions sweet, like licorice and banana; the high tones thin and insipid in tastea mixing, as you see, of taste reactions with hearing sensations.
Sometimes hearing is mixed with the sensation of clouds floating before the eyes. These are called “photisms.” As a piece of music is played by a piano or by an orchestra, the subject of photisms can close the eyes and enjoy a vivid interplay of colors, as clouds float before the vision, constantly changing and mingling like wreaths of smoke. And, as a matter of fact, various well-known musical compositions are characterized by color designations. Thus Liszt’s Etude, “Waldesrauchen,” is green because, of course, leaves of the woodland trees are green.
Of the various theories to account for synesthesia, none is entirely satisfactory. The individuals who possess it are usually intelligent, imaginative and sensitive. In short, they have a highly organized nervous system. The condition tends to disappear as the subject gets older and, as has been suggested, this may be due to the fact that it serves no useful purpose in the life of the organism.
It would be wrong to suppose that these conditions can be induced by imagination. Color sensations have to be associated with music, and the same note or the same composition will invariably provoke the same visual response.