BBC radio documentary programme on the relationship between sound and colour explores Isaac Newton’s “optickal” theories…
“Music in the 17th and 18th centuries and long before wasn’t just the sound we heard, it was a bigger binding idea of a universal system of proportions, and ratios that connected the cosmos together”.
http://www.bbc.co.uk/programmes/p04dv0ns
Kadinsky later in the 20th century wrote
“Colour is the keyboard, the eyes are the harmonies, the soul is the piano with many strings. The artist is the hand that plays, touching one key or another, to cause vibrations in the soul”.
Pictured is Composition V11, 1913 by Wassily Kandinsky.