This biographical movie about the life and music of Jerome Kern has a number of good sequences that make it worth watching. A great deal of the movie consists simply of recreations of stage numbers from Kern's many musicals, and indeed these account for many of the best parts of the movie. It also adds a light and highly stylized account of his career, which is often bland, but occasionally has some nice moments.
It starts with Kern, at the height of his popularity, attending the opening of "Show Boat", and it features a lengthy staging of portions of that show. From there, it has Kern telling the story of his career up to that point, his work with a fictional mentor and later with collaborator Oscar Hammerstein, and his marriage. These episodes are frequently interlaced with more musical numbers of varying lengths.
The pattern works well enough in general, as something of a slight variant of the usual musical format. The main flaw is that it is really a bit too long for the material it contains. Much of it has little real substance as a story, and it works better as light entertainment. It does at times touch on some real issues, most particularly in following the mentor's daughter as she grows up.
Robert Walker is solid as Kern, and Van Heflin gets some good moments portraying the wise, slightly grouchy mentor. But some of the best moments are provided not by any of the main characters but by stars like Judy Garland, Lena Horne, and June Allyson, who appear in the musical numbers. Most of these are enjoyable, and a couple of them are show-stoppers. They probably provide the main reason for watching the movie as a whole.