The Jesuit mathematician Louis Bertrand Castel announced the clavecin oculaire in 1725: a harpsichord whose keys would raise colored displays, so the deaf might enjoy harmony and the eye might learn what the ear knew. He built demonstration versions over the following decades; contemporaries including Telemann took interest, and satirists took aim.
Castel mapped notes to colors by analogy with Newton’s spectrum-scale correspondence, starting from blue at C, and argued the eye deserved its own music of color succession.
The instrument barely worked with candlelit technology, but the proposal set the template every color organ since has followed: a keyboard where light is the voice.