According to art critic Carter Ratcliff,[1] "His paintings usually erect a visual architecture sturdy enough to support an array of standing, riding, levitating figures.
According to the poet John Ashbery,[2] Müller "brings a medieval sensibility to neo-Expressionist paintings."
In 1933 his family fled the Nazis to Prague, and later to Bex-les-Bains, Switzerland;[3] there he experienced the first of several attacks of rheumatic fever.
Shortly after the fall of Paris, Müller was released, at which time he moved to Ornaisons, near Narbonne.
Following an unsuccessful attempt to escape to the United States from Marseille, he was able to cross the border into Spain in 1941 and proceed via Portugal to New York.