music intended for instrumental performance in conjunction with a simultaneous projection of changing colours onto a screen. It has its origins in the theory, prevalent in the Renaissance and systematically set forth by the 17th-century Jesuit music theorist and mathematician Athanasius Kircher (Kircher, Athanasius) (1602–80), that each musical sound has a necessary, objective correspondence to a certain colour. From the 18th to the 20th century, experiments were made by adapting various keyboard instruments in such a way that when a key was depressed it would, in addition to producing a sound, raise a coloured tape or glass through which light was projected on a screen. Several modern composers, notably Arnold Schoenberg and Aleksandr Scriabin (Scriabin, Aleksandr), were attracted by the idea and produced examples of colour music.