A Good Explanation

Sound → color synesthesia

In sound → color synesthesia, individuals experience colors in response to tones or other aspects of sounds. Simon Baron-Cohen and his colleagues break this type of synesthesia into two categories, which they call "narrow band" and "broad band" sound → color synesthesia. In narrow band sound → color synesthesia (often called music → color synesthesia), musical stimuli (e.g., timbre or key) will elicit specific color experiences, such that a particular note will always elicit red, or harps will always elicit the experience of seeing a golden color. In broadband sound → color synesthesia, on the other hand, a variety of environmental sounds, like an alarm clock or a door closing, may also elicit visual experiences.

Color changes in response to different aspects of sound stimuli may involve more than just the hue of the color. Any dimension of color experience (see HSL color space) can vary. Brightness (the amount of white in a color; as brightness is removed from red, for example, it fades into a brown and finally to black), saturation (the intensity of the color; fire engine red and medium blue are highly saturated, while grays, white, and black are all unsaturated), and hue may all be affected to varying degrees (Campen & Froger 2003). Additionally, music → color synesthetes, unlike grapheme → color synesthetes, often report that the colors move, or stream into and out of their field of view.
Like grapheme → color synesthesia, there is rarely agreement amongst music → color synesthetes that a given tone will be a certain color. However, when larger samples are studied, consistent trends can be found, such that higher pitched notes are experienced as being more brightly colored (Ward, Huckstep & Tsakanikos 2006). The presence of similar patterns of pitch-brightness matching in non-synesthetic subjects suggests that this form of synesthesia shares mechanisms with non-synesthetes (Ward, Huckstep & Tsakanikos 2006).


(music to be added later)