Mahler a Venezia
Luchino Visconti‘s Morte a Venezia is one of those few films that successfully manage to translate a book into cinema. When planning the film’s soundtrack, Visconti chose Mahler, whose death in 1911 partly inspired Thomas Mann’s novella. The main theme used is the 4th movement (Adagietto – sehr langsam) of Mahler’s 5th Symphony.

There’s a great anecdote about the soundtrack found in Bogarde’s biography at IMDB:
“when the lights went up in a Los Angeles screening room after a showing of “Death in Venice” for American executives, no one said anything. The silence encouraged Visconti, who believed it meant that the executives were undergoing a catharsis after watching his masterpiece.
However, he soon realized that, in Bogarde’s own words, “Apparently they were stunned into horrified silence.. A group of slumped nylon-suited men stared dully at the blank screen… One nervous executive, feeling something should be said, got up and asked: “Signore Visconti, who was responsible for the score of the film ?” — “Gustav Mahler“, Visconti replied. ” — “Just great”, said the nervous man. “I think we should sign him…”
Michael Chanan wrote in more detail about the links between Mann and Mahler in an article for Music and Musicians.
Death in Venice has become arguably Thomas Mann’s most famous and widely-read work. (Let’s face it, few people have the time and patience for Mann’s long-form novels like Buddenbrooks or Der Zauberberg.)
Similarly, Mahler’s 5th is undoubtedly the most-heard and widely-performed of his symphonies. After its premiere in Cologne in 1904, Mahler is reported to have said “Nobody understood it. I wish I could conduct the first performance fifty years after my death.” Thomas Mann might have shared comparable sentiments about his novella…

Björn Andrésen (Tadzio) and Dirk Bogarde (Gustav von Aschenbach)