6- shares two of the tonic's three notes — swap it in where a section used to start on 1 and the whole passage darkens without a single new note. The last-chorus minor dip is this move wearing a cape.
movessame family notes, but the floor steps down to 6 — the room dimssolo·singmelodies survive the swap unchanged — that's the whole trickon recordthe last-chorus minor dip — a pop arranging staple for fifty yearstry itTake a 1 → 4 → 5 verse and play it once as 6- → 4 → 5. Same song, new weather.