There is a scene I love in the John Sales movie "Matwan". In a workers camp there is a guitar player on his porch that stars a melody. A few cabins over a black hamonica players starts a counter melody and soon an Italian worker on his porch nearby starts playing his mandolin along with them. To me it was symbolic of the melting pot of American music. We've become a melting pot with our music if not our society. Great movie about union organizing.

I assume you weren't asking for titles of movies like "Wasn't That A Time" about the Weavers.