Kirk Douglas's trumpet licks were performed by Harry James, who also taught Douglas the correct fingering of the instrument.
While making this film, Kirk Douglas tried to warn Doris Day about taking financial advice from her then manager Martin Melcher. Douglas had gotten burned by Melcher, and thought Day naive to be so trusting of him. Not only did Day ignore Douglas' advice, she later married Melcher and, after his death in 1968, discovered that he had both squandered the fortune she had earned during her 20-year film career, and left her seriously in debt to the IRS.
The film was a reunion of sorts for Lauren Bacall and Hoagy Carmichael, who co-starred six years previously in her first film, Le Port de l'angoisse (1944).
The film was released in Australia as "Young Man with a Trumpet" on censorship grounds. At the time, the word "horn" in that country was slang for the male erection. This may also be the reason why the film was released in Britain as "Young Man Of Music", although it is more likely that the notoriously hidebound British censors simply didn't understand what "horn" meant and assumed that cinema-goers wouldn't, either.