Everyone went to the new movies; even the austere Schoenberg was a fan. American dances and fashions established new courtship rituals. Josephine Baker danced, Bessie Smith sang. Louis Armstrong blew his trumpet. The end of war gave rise to a glimmer of a future multiculturalism, a tolerance gently evoked in the blackface Ernst Krenek opera Jonny spielt auf, more so perhaps than in Al Jolson's The Jazz Singer. 

The American in Paris was born. Three generations of composers—from Aaron Copland to Ned Rorem and Philip Glass—sailed over to attend Nadia Boulanger's finishing school. Ernest Hemingway and his friends, aimless in the aftermath of war, found a centre of gravity in Gertrude Stein. Artists flocked to the sexy squalor of Montparnasse where, as Jean Cocteau quipped, "poverty was a luxury". Racism, Prohibition and the return of puritanism provoked a flight of young artists from America, just as American culture was ascendant in Europe. The more American art engulfed the European continent, the more Americans looked to Europe for cultural legitimacy. In Hollywood, the biggest male star was English, the female Swedish. The preferred accent in American talkies was British. 

These transferences and transformations were a direct outcome of the paralysis and mayhem of the First World War. More than just a transient response, they provided the template by which art would respond to war ever after.

Those gaping mouths of George Grosz's grotesques, made in the aftermath of the First World War, become Francis Bacon's three screaming popes after the Second. The anarchic fatalism of Jaroslav Hašek's Good Soldier Svejk is repeated in Joseph Heller's Yossarian in Catch-22. The crashing cluster tones of Bartók's piano sonata, struck with the full forearm on the keyboard, anticipate the heavy metal amplifications of Vietnam and Apocalypse Now. Art had delivered a response to war, appropriate and unmistakable.

Schoenberg emerged from the trenches dissatisfied with free atonality. He replaced it with the strict discipline of a 12-note serial row—a method, he said, "that will ensure the supremacy of German music for the next hundred years". His synthetic serialism, augmented by Anton von Webern to include intervals, dynamics and every other musical element, became the fundamentalist benchmark for the avant-garde that arose in the aftermath of the Second World War-the ascetic tendency of Pierre Boulez, Karlheinz Stockhausen and the pleasure-hating Darmstadt school. In much the same way, the Californian nihilism of John Cage, incubated  between 1939 and 1945, would become the template for the repetitive minimalism that arose during and after America's Vietnam War. Art was no longer impassive.