Synaesthesia is a condition where two or more senses cross. For instance, some people can "see" smells, "feel" words, or associate certain numbers with colours. My synaesthesia is sound-colour: When I hear a sound, I experience a colour associated with it. Often, I am not able to name it, but there is always a strong sense of the sound being a colour, and of it being different to that of other sounds. It has been suggested that this may be due to my never having learnt colours, having lost my sight too early; the few occasions on which I can name the colour, meanwhile, may result from my having been told, before I lost my sight, that something was, for example, blue or green.
I find synaesthesia extremely useful, particularly in learning and composing music. Because each note is a different colour, (even the same note in different octaves), and because the dynamic, timbre and articulation of the note also influence the colour, it is almost as if each note is "highlighted" differently, making it clearer and therefore easier to internalise. In a similar way, I find that when I compose, I am as much creating a piece of visual art as I am a piece of music.
If you are interested to find out more about synaesthesia, and to take part in research, click here.