Rhapsody in Blue
Starring Robert Alda, Joan Leslie, Alexis Smith, Charles Coburn, Julie Bishop, Albert Bassermann, Morris Carnovsky, Rosemary DeCamp, Oscar Levant, Paul Whiteman
It's a documentary and musical movie, and has a rating of 7 out of 10 from Imdb which is usually fine for this kind of movie.
Watch it here
Not found streaming from Germany.