Gary Oldman actually played all of the Beethoven pieces he performed in the film. A different musician performed in the official soundtrack. When Oldman learned he would be playing the lead role, he spent six weeks practicing on a Steinway piano for six hours a day in his hotel, and completely immersed himself in the music as his research for the character. In an interview with the South Bank show in 1997, Oldman quoted an article that said "he mimes very well" in the film. He then laughed and said "I'm playing it! I can play that!"
Bernard Rose removed the music from the Columbia and Focus opening segments. He thought they sounded "cheesy" compared to Beethoven.
Beethoven's remarks to Schindler during their first meeting, at a rehearsal of the Kreutzer sonata, is taken from Tolstoy's short story "The Kreutzer Sonata".
When Beethoven believes he is alone and starts playing the first movement of his 14th sonata ("Moonlight"), what is heard is unmistakably played on a modern piano. However, it wasn't possible for pianos of the time to play the piece as Beethoven intended, meaning that he never actually got to hear the piece as he imagined it when written. This was actually the case for many of Beethoven's works; he was known for pushing the boundaries of what was possible on several instruments.
In real life, Schindler was not a close friend of Beethoven, though he was Beethoven's secretary for a while. It has been claimed that Schindler destroyed 260 of Beethoven's approximately 400 conversation notebooks, although this belief has been challenged in recent years, and forged entries into the surviving ones. Beethoven's actual eulogy was written by poet Franz Grillparzer and given by actor Heinrich Anschütz.