It’s the second most recorded song in history–and it’s a hell of a lot weirder than you thought. Depending on who’s playing it and who’s listening, the key that it’s played in has a lot of cultural significance. So that’s a whole thing. But the song still has one of the most recognized melodies in the world–which is weird, because when you break down the musical grammar of the most popular arrangements, you find some elements that are written but only hinted at when performed, or elements that are frequently performed that weren’t written. It’s a song that’s sort of a weird echo of itself.