One of Glenn Miller's trombones is on display at the National Museum of the US Air Force in Dayton, OH, along with other Miller memorabilia. According to the display notes, the Miller estate allowed James Stewart to "play" this trombone in this film. Another trombone and additional memorabilia are displayed at the Glenn Miller Birthplace Museum in Clarinda, IA.
James Stewart took trombone lessons in order to actually play during scenes where Glenn Miller is seen performing with his orchestra. However, while learning from his tutor, Stewart's attempts at practicing the instrument made such horrible noises that the teacher reportedly went home in a rage every night to his family. It was decided that Stewart would accurately mime the motions of playing (especially apparent during the performance of String of Pearls) while his trombone tutor Joe Yukl did the actual playing.
Among those attending the premiere of the film was Glenn Miller's mother, who thought the film good enough, but opined that her son was better-looking than James Stewart.
Although, at the time of filming, James Stewart was only two years older than Glenn Miller when he died, it also meant that he was 46 when portraying the young Miller in his early twenties. June Allyson was 37 when playing the 22-year-old Helen.
Due to a cessation of the professional relationship since about 1950, singer and saxophonist Tex Beneke does not appear in this film. His vocal lead on "Chattanooga Choo Choo" as well as his distinctive tenor sax sound on In the Mood and other classic Glenn Miller recordings are missing from the soundtrack. The parting was due to Beneke's leadership of the Glenn Miller "ghost orchestra" during which he tried to put his own distinctive spin on Miller classics, resulting in the Miller estate ending his contract as band leader.