If you ever watched any documentary about the Nazis, you certainly have heard the Horst Wessel song.
Oh, sure I have. Just didn’t recognize the name.
Also, if you remember the first "Blues Brothers" movie, "Horst Wessel" is the music you hear playing in the scene where Henry Gibson is painting the eagle statuette, just as the Gruppenfuhrer comes in to report that he's traced Elwood's license tag.