How did the the two men befool the people at the party?

The men, who were German, told the party guests that their friend, the piano player, played a song that was the funniest they'd ever heard. They then convinced the party goers to request the song, which they did. When the entire room exploded with laughter, the pianist became angry and stomped out of the room..... the song was a tragedy, but the guests wouldn't know that, as they didn't understand German. The two Germans, subsequently, had a good laugh over the success of their practical joke and made a quick exit.