 In 1999 , BBC producer Rodney Wilson asked Stockhausen to collaborate with Stephen and Timothy Quay on a film for the fourth series of Sound on Film International . Although Stockhausen 's music had been used for films previously ( most notably , parts of Hymnen in Nicolas Roeg 's Walkabout in 1971 ) , this was the first time he had been asked to provide music specially for the purpose . He adapted 21 minutes of material taken from his electronic music for Freitag aus Licht , calling the result Zwei Paare ( Two Couples ) , and the Brothers Quay created their animated film , which they titled In Absentia , based only on their reactions to the music and the simple suggestion that a window might be an idea to use ( Anon . 2001 ) . When , at a preview screening , Stockhausen saw the film , which shows a madwoman writing letters from a bleak asylum cell , he was moved to tears . The Brothers Quay were astonished to learn that his mother had been " imprisoned by the Nazis in an asylum , where she later died . … This was a very moving moment for us as well , especially because we had made the film without knowing any of this " ( Aita 2001 ) . 
