"Gloomy Sunday" (1999) (Ein Lied von Liebe und Tod).
From imdb: "Budapest in the thirties. The restaurant owner Laszlo hires the pianist András to play in his restaurant. Both men fall in love with the beautiful waitress Ilona who inspires András to his only composition. His song of Gloomy Sunday is, at first, loved and then feared, for its melancholic melody triggers off a chain of suicides. The fragile balance of the erotic ménage ŕ trois is sent off kilter when the German Hans goes and falls in love with Ilona as well. "
There is a wonderful scene in which the woman is out with one of the two men, and the other man sees them together. She kisses each of them in turn, and from then on they just accept that they both love her and she loves both of them.
Also contains one of the best subtitle errors I have ever seen: "Clam yourself!"