Ooooooh, now that's a challenge. I don't think I've ever tried to sing this song from memory.

As it is, even with the song playing, I tend to fumble the line right after "Helter Skelter in the summer swelter/the Byrds flew off with the fallout shelter/Eight miles high and falling fast." I think it's because McLean breaks the song's cadence on "fast" and does something a little bit different, which tends to garble the next line for me.

But it is scary, isn't it? I know you're younger than me, and you and fellow your high school theater rats could sing this song from memory.