I am about to put the lid down on the piano keyboard in my 6th-grade music class when a particularly animated student runs up to me and says excitedly, “Teacher, I can play ‘Für Elise’!” I encourage her to do so, but the result is just the famous first four notes, an E and the D-sharp below it, repeated, played back and forth in endless seesaw. I tell her I think there’s more to it than that, but she is happy just knowing the first notes. Though not particularly musically gifted, nor a fan of much music outside of pop, she is mesmerized by this little classical piano piece written more than 200 years ago. So are millions and millions of others. The popularity of Beethoven’s intermediate-level bagatelle (something like “a trifle” or “simple piece”) is astonishing. I can count on the fingers of one hand the number of my …