Interaction between different spheres of the arts was important to the Symbolists. Works often contained references to music, and compositions underlined harmony between form and colour.
In the early 20th century many artists grew interested in theosophy and search for the spiritual, leading partly to more simplified and abstract expression.
In his major manifesto Concerning the Spiritual in Art (1911) Wassily Kandinsky wrote of the unity of colour, feeling and music: ”Colour is the keyboard. The artist is the hand playing, falling variously on the keys and causing the soul to vibrate.”