When Gershwin and Professor Franck are discussing whether George should go to Europe to study, Franck makes fun of George's necktie and pulls it out of George's jacket. However, when they turn to look at the busts of classical composers, the tie is neatly tucked back inside the jacket.
After Christine brings the terrier Tinker for George, when the camera angle is on George, Tinker's head is pointing up and his mouth is open. When the camera angle is on Christine, Tinker's head is level and his mouth is closed.
While Max is making drinks at George's welcome home party he has his cigar in his right hand and puts it down. Switch to a behind shot and he has the cigar in his left hand on the soda bottle. Switch to a front shot and the cigar is now in his mouth.
Chico Marx is referred to early in the film. Gershwin mispronounces the name as "CHEE-ko", which generally continues to this day. Chico's name is correctly pronounced as "CHICK-o".
In Max Dreyfus' office, Oscar Levant while looking at Georges' score of "Swanee" hums a perfect forth (D down to A) and says, "A diminished 9th." In the next scene Max Dreyfus also refers to the uniqueness of a diminished 9th. In Swanee there is no diminished 9th. There are enharmonic equivalents ie. a C# melody against a Db bass which sounds like a diminished 9th. It is acually a sharped major 7th. The interval of a diminished 9th ie. (C up to Dbb or C# up to Db)does not happen in Swanee. Both a diminished 9th and an enharmonic equivalent will sound like a perfect octave when played eight notes apart.
The aria, "Summertime", from "Porgy and Bess", is performed first by the character Clara, and later, in a tragic scene, by Bess. But not only by Bess, as the film seems to depict. The film also gives the impression that the first verse is performed by chorus, which is not the case. The chorus only hums an accompaniment.
The opening credits say "Music and Lyrics by George Gershwin and Ira Gershwin", which correctly shows that George wrote the music and Ira wrote the lyrics. DuBose Heyward, who wrote the lyrics to "Summertime", is not credited.
After the first time we hear the song Rhapsody in Blue in the theater, the camera pulls back so we can see the audience in the balcony, but they are not clapping because they are cardboard cutouts.
When Mr. Kast storms out of his office to fire George Gershwin, the camera's shadow is visible.
George is seen painting a portrait while wearing a silk smoking jacket right inside his luxurious penthouse apartment. This would not happen in reality. Oil painting is very messy, and the pigments are impossible to get out of fabric and carpeting.
The performance of "Concerto in F" is interrupted to announce Gershwin's death. While this was obviously done to give Levant a "the show must go on" moment, in real life they would have respectfully waited until it was finished, especially as it was only a few bars from completion.
Robert Alda had a lot more hair than the real Gershwin did.