In August 1952 Mario Lanza recorded the soundtrack. The whole recording was done in single takes. Every phrase in it was Lanza magic at its best. However, on the film set things were not to go well at all. The first scene to be shot was the song "Beloved" on the terrace. Director Curtis Bernhardt did not like the way the song was sung and corrected Lanza, telling him that he was putting too much emotion in his singing instead of sounding more stuffy and rigid like a Prussian prince. Lanza informed Bernhardt that he was to direct only his acting, and that Lanza's singing was strictly Lanza's department. Bernhardt would not accept this, and Lanza would not be told how to sing by a movie director. The end result was that Lanza walked off the set and vowed not to return as long as Bernhardt was the director. The studio took an injunction against Lanza for damages and losses. He could not perform in public, on radio, or in the recording studio for the remaining time of his contract with MGM (which was then 15 months). A solution was reached in May 1953: the studio would remove the embargo on Lanza if he would allow his voice to be used while another actor played the part of the prince. This was agreed to and the filming got under way with Edmund Purdom lip-synching Lanza, which he did marvelously. The irony is that when the film was finally made, the director was no longer Bernhardt, but Richard Thorpe, who had worked harmoniously with Lanza on The Great Caruso (1951).
Despite a request by producer Joe Pasternak, the mentor of her early film career at Universal, Deanna Durbin would not come out of retirement to play the role of Kathie the barmaid.
While the basic story remained unchanged, the movie made many changes from the original operetta. 14 of the original songs were eliminated, 3 new songs were written and almost all of the original lyrics from the remaining songs were replaced. In the stage version, the song "Just We Two" is sung by the Princess Johanna and a character who does not appear in the film, Count Tarnitz. She and Tarnitz are secretly in love but must part for state reasons. In addition, the time span of the play (more than two years) was reduced to only a few months in the film.
The Prince and Count von Asterburg fought a duel in which the Count received a cut on the cheek, which another student commented that the Count was very proud of. Students at Heidelberg University fought duels with each other often seeking to receive a blow on the cheek with a saber which caused a scar, as a mark of bravery to be proud of. These were actually known as Heidelberg dueling scars. The practice was so formalized that duels were fought with sabers with only one small sharpened area of the blade to leave a cut, and dueling masks with slits over the cheekbones to allow for the scarring cut. The film depicts a duel with normal sabers and no masks, which would have been quite unusual.