It’s rare in popular music, but any bit of a song might abruptly shift you mentally to an unexpected and busy place, like when the special cookie unleashes a flood of remembrance in Proust. Would that necessarily be a personal, private event, or could it befall all of us together? I have an example where I suspect, or hope, it isn’t just me.
In “A Song For The Dead” by Queens of the Stone Age, the chorus contains a familiar rock four-chord sequence (especially if you’ve been listening to the Doors or Black Sabbath—it’s very sinister-portentous), except that something odd happens with the fourth chord. The first three are C, D-flat, and E-flat. We expect to finish with a B-flat minor, which would reinforce the D-flat feeling from chord #2 since a B-flat minor contains a D-flat note as its third. But what we hear is a B-flat major chord featuring a D instead of a D-flat, which gives us a sunny lift.
On paper it seems a subtle difference, but in the ear it’s startling. The B-flat major makes us feel we’re completing the four-chord sequence of a song with drastically different associations than those of the somber minor-chord sequence we thought we were in.
Part of the changed meaning is social. We’re shifting from an anguished contemplation of individual doom to a cherry-flavored plunge into flower-powered community, to a song that feels more like, oh, “Pictures Of Matchstick Men” or “Waitin’ For The Wind.”
What’s up thematically? The song ostensibly offers “the study of dying/how to do it right.” We’re being carried through the clouds of fear and loss to the B-flat major rainbow of salvation. Can I really be dropped off at heaven at the end of a four-chord line, over and over? That’s hard to believe in! Are the Queens kidding? Probably. Maybe not.
The sequence of the first three chords is so strongly deterministic that the fourth chord’s different implication always comes as a shock; and the fourth chord and its associations are so strong that it always stands up against the force of the preceding three and pours its new meanings all over them. We hear this 12 times in the course of the track. The effect doesn’t weaken.
Because we feel a social charge in the B-flat major we have a heightened sense of the chordiness of this chord, the mutually supportive ringing of its notes, the active sharing of its aura. Possibly something bigger is being revealed to us. To teach us what makes a world, that incredibly rich composition, maybe a designated heaven needs a moment of our attention.
 The D-flat chord is on a continuing C root, so with that second chord there’s an ambivalence about going upward; that temporary repression of progress toward the E-flat chord gives us a sense of bobbing up into it forcefully when it arrives, an extra energy that gets harvested by the surprising fourth chord.