Christoph Koncz (as Kaspar Weiss the orphan virtuoso) was only nine years old when featured in this movie. He is an Austrian-Hungarian classical musician that became an internationally-renowned violinist and conductor.
Joshua Bell, who was the solo violinist on the sound track, was also a violinist double. When non-musician actors needed to be shown playing the violin in close-up, Bell would hide behind the actor, and his left hand would be the hand seen by the camera on the neck of the violin. According to an interview with Bell on National Public Radio, he was scolded several times by Director François Girard for overacting.
The movie was inspired by the Stradivari violin known as "The Red Mendelssohn".
When Frederick Pope (Jason Flemyng) leans back in the tub with the letter from his lover in his hand, the shot is a re-creation of the famous painting "The Death of Marat".
When Frederick Pope (Jason Flemyng) prepares to play his original, inspired piece in the rotunda, just after the conductor raises his staff, you can see Joshua Bell (who is the actual solo violinist who performed on the movie soundtrack) as one of the violinists in the orchestra.