From the movie Dangerous Moonlight (1941). A stunning American reporter meets a Polish Air force officer amid the newly bombed ruins of Warsaw at the outbreak of WWII. He is a concert pianist and in this clip is in the process of composing, what will be by the end of the movie, the "Warsaw Concerto". Not a real Concerto - just a Pastiche in the Rachmaninoff style -- written specially for the movie by Richard Addinsell.
Walbrook does a poor job of faking playing the piano which on the soundtrack was actually played by un-credited Louis Kentner.
This is a cute scene where the bombing of Warsaw at the outbreak of WWII forms a somber backdrop to a beautiful piece of music.