Cat and Bird
Klee was started out on the path to be a musician and began playing the violin at eight. At that time he was also given a box of chalk by his grandmother and encouraged to draw. I think there is something musical about his compositions, maybe because of this. Especially I can see the influence of the string instruments in his work.
Klee worked with many different types of media—oil paint, watercolor, ink, and more. He often combined them into one work becoming the father of mixed media. The above painting is done on fabric pasted to a board. He has been associated with expressionism, cubism and surrealism, but does not fit into one school of art.
His works, like the Cat and Bird one, often have a fragile child-like quality to them and are usually on a small scale. They frequently allude to poetry, music and dreams and can include words or musical notation. His later works, which are my personal favorites, are distinguished by spidery hieroglyph-like symbols which he famously described as "taking a line for a walk".
As illustrated in this work entitled Contemplating.
Or this work called The Twittering Machine.
Yellow Birds and is my favorite.
For more information on Paul Klee see Wiki.