Personally, I can't feel sad when hearing Puttin' on the Ritz. It's a happy song.
But what makes you sad? Is it the fact that he's playing all alone and people are walking by?
Also, I find the title of your post inspirational, for some reason. It made me think of the title to an interesting novel. I want to try to write a story with that title: ''A lonely man playing a fire spitting trumpet on the street made me sad''. Just wondering what could be the plot. Maybe there would be no plot, just a lonely man playing a fire spitting trumpet on the street that made someone sad.