A favorite of mine to teach the idea of "Theme and variations". Often, people have a hard time with this concept, since the theme and the variations often don't sound anything like each other after, say, the fourth or fifth iteration. With this piece, I keep people guessing which piece of music is the theme, like an extended musical riddle, because the theme comes last. Every so often I'll drop a hint.
"It's a British Folk Song."
"You know it already, it's not classical."
"It sounds like someone walking in the snow, here, but it's a dance."
"No, it's not rock."
My favorite response came from an old Navy man after The Reveal: "I really should have known that!"