It turns out that Orff, who was born in Bavaria in 1895, had a Jewish grandmother [OK, that's not what I mean by despicable - ed.] – a fact that, extraordinarily, he managed to conceal from the painstaking research of the National Socialists. "Once you tell one lie to cover up a lethal situation – one Jewish grandparent was enough to condemn you to death – it's a slippery slope," comments Tony Palmer. "Ever more must be done to maintain the deception."

The lies went on. Orff later claimed that the Nazis had banned Carmina Burana. Nothing could have been further from the truth – they adored it, and no wonder. Its simplicity, accessibility and primal force exemplified the opposite of the atonal or serialist works that the regime deemed "decadent" (entartete musik). Indeed, the work – premiered for the Nazi party in 1937 – helped to draw Orff to their attention and won him support from the Reich. Nor was he above writing new incidental music to A Midsummer Night's Dream when the much-loved work by the Jewish Mendelssohn was banned.

Orff, however, was never a card-carrying member of the Nazi party and privately despised them for their crudity and philistinism. "He wasn't interested in politics," his second wife, Gertrud, recalls in the film. She adds that the war was "not our fault", but that they did not protest because it "wasn't safe".

It is telling that one of the works closest to Orff's heart was a Märchenopera (fairy-tale opera) that he wrote in 1939: Der Mond, telling of a world plunged into darkness when fiends steal the moon. It contains some of his most appealing music, but proved unstageable except by a puppet theatre. Many artists, comments the historian Michael H Kater, felt that "the regime had stolen the light" from them. Still, it was not difficult for the previously penniless and struggling Orff to see that the Reich had high hopes for him. By 1943, his name was on a special list of favoured artists; he was not to be conscripted, he received a 2,000-mark prize from the Cultural Chamber in 1942 and he was placed on an elite payroll that gave him 1,000 marks per month. Germany's two senior composers, Richard Strauss and Hans Pfitzner were ageing and would soon die; it was clear that if Germany were to win the war, Orff would quickly become the Reich's leading composer.

One can argue that, like so many living under insane and tyrannical regimes, Orff merely did what was necessary in order to survive. And perhaps it was his good fortune that when he found himself facing the "de-Nazification" process after Germany's defeat, his interrogator was a musically educated admirer. This American intelligence officer, keen to help him, asked him simply to provide something, anything, that could show he had spoken out against Hitler.

Orff's invented response at this moment would never cease to haunt the composer.

Kurt Huber, professor of philosophy at Munich University, had provided Orff with the medieval Latin texts that he set in Carmina Burana; the two had also worked together on Der Mond. In 1942, Huber and a core group of students formed the White Rose resistance movement which distributed pamphlets calling for active opposition to the Third Reich. Huber authored the sixth and final leaflet. Huber's widow, Clara, relates on camera that Orff was a close friend and used to visit them every Sunday. Yet, she adds, he had no part in the movement and never said a word against Hitler.

On the contrary, the day after Huber's arrest by the Nazis, when she told Orff what had happened, his response was: "I am ruined! Ruined!" She hoped he would use his influence to intervene on her husband's behalf; but Orff did nothing. "He thought only of himself," she recalls. She never saw him again.

Put on the spot by the de-Nazification interrogator, Orff falsely claimed that he had co-founded the White Rose movement with Huber. The group's members, including Huber, had been executed in 1943. Nobody was left alive to dispute his words and he walked out with a clear name. He only had to answer to his conscience.