In the final scene which takes place in a recording studio, the reaction shot of Hoagy Carmichael is actually taken from an earlier scene in a dance hall.
Rick Martin is alone in a recording studio, and in a rage, he tries to destroy his trumpet by banging it on a nearby table and chair. When the trumpet doesn't shatter, Martin throws it to the floor, and the trumpet bounces out of frame, clearly in one piece. When the scene cuts to an overhead shot of Martin sitting at the table a shattered trumpet is lying at his feet in several pieces.
Early in the movie when young Rick Martin is walking on the street, a car pulls up to the intersection. Although it on screen only for a moment, it appears to be late 1940s or early 1950s Hudson. This would match the time that the movie was made but would not be right for a boy who ages 15-20 years to become Rick Martin the man.
When a young Rick Martin is looking out the rear window of the car as it drives away from the cemetery, a light or reflector and its articulated stand is clearly reflected on the glass.