After returning home, Klee painted his first pure abstract, In the Style of Kairouan (1914), composed of colored rectangles and a few circles.  The colored rectangle became his basic building block, what some scholars associate with a musical note, which Klee combined with other colored blocks to create a color harmony analogous to a musical composition. His selection of a particular color palette emulates a musical key. Sometimes he uses complementary pairs of colors, and other times "dissonant" colors, again reflecting his connection with musicality. 
Paris-based abstract art movement most often referred to as Orphism , whose style featured loosely painted patches of rainbow colours. The name (Orpheus was a mythological poet and musician of ancient Greece) was coined by French art critic Guillaume Apollinaire when describing the 'musical' effect of the abstract paintings by the Cubist Robert Delaunay (which comprised overlapping planes of contrasting or complementary colours) in order to distinguish them from Cubism generally. Delaunay himself used the term Simultanism to characterize his work. Another exponent of Orphism was the French-Czech painter and anarchist Frank Kupka, one of the first to create genuine abstract art, characterized by solid geometric blocks of colour. The style was very similar to Synchromism , a method of painting launched in Paris in 1913 by two American painters, Morgan Russell (1886-1953) and Stanton MacDonald- Wright (1890-1973).