In 1964, Glen Campbell joined the Beach Boys to replace Brian Wilson while he recovered from a nervous breakdown. Brian returned the favor with this gorgeous song.

Telling the truth—no matter how hard, how naked and deep—is what every great artist aspires to do. Glen Campbell has been such an American icon for so long, but it’s important not to forget the substance and self-reflection that has driven the bulk of his work. Even his megahit “Rhinestone Cowboy” was about someone small-time dreaming of the big time, and by singing it, Campbell humbled himself to what he used to be: a kid from Arkansas who came to Hollywood to play guitar and sing his songs. He hadn’t forgotten.

And that’s why his great act of bravery—of saying his final goodbye to the world in song by way of a video—is exactly in line with who Glen Campbell is. But of course anyone who has loved him as a fan couldn’t help but be devastated by it, and think, “Well, I’ll miss you . . .”

Glen Campbell had the good sense to record Jimmy Webb’s songs like “Wichita Lineman” and “Galveston,” giving the world hits that had lyrical beauty and intelligence, but still made us want to head out on the road and into a star-filled night. And early on, he cut this: a song  The Beach Boys’ Brian Wilson and songwriter Russ Titelman wrote for him. “Guess I’m Dumb” is nothing close to country; it’s a big masterful pop production produced by Wilson and recorded in Hollywood, U.S.A., with lots of horns, some strings, and backup singers. It sounds like a lost Burt Bacharach track, or like it would fit right in on the next year’s Pet Sounds. And he’s right in the middle of it: telling the truth.