Synesthesia encompasses a wide variety of phenomena that involve mixed neurological sensations, for example, when seeing a certain letter of the alphabet evokes (or causes one to see, which then overlaps the figure) a particular color without fail, automatically; see also Mixed Signals for information and descriptions of a wide variety of types.

When a synesthete (someone with synesthesia) has a sound-to-color association (or projection), specific keys and instruments will evoke certain colors (as with grapheme-to-color synesthes), sometimes even effecting them visually- perhaps seeing the colors in their field of vision, moving and changing.

I personally am a sound-to-color synesthete, though I am an ‘associator’ and not a ‘projector’- I don’t see the colors in front of me, but they have always cropped up in my mind whenever I am listening to any piece of music, as well as my own music. Although my synesthetic experiences are likely far from being universal, I will sometimes try to guess the color of a band’s album cover I haven’t seen before after downloading a song, based on what colors are popping into my mind- and sometimes I’m on target!

I’ve combined some of the colors reflected in favourite songs of mine (automatically associated) with patterns from the excellent COLOURlovers because they seem to convey the vibe of the song:

(Franz Ferdinand)

(My Bloody Valentine)

(Joy Division)

(Death From Above 1979)

(Suicide)

(Blur)
I plan to expand on this subject in the future- if you have had experiences with synesthesia or any questions or remarks, comment away!