"Noble rot". What a beautiful phrase. It refers to the infection of wine grapes by a groovy parasitic fungus called Botrytis cinerea. There's an excellent writeup in botrytis that gets into detail about that. My sources inform me the Sauternes of France and and the Tokay of Hungary benefit from this stuff.
But let's just ogle it for a while, if we may. That funny looking stuff in gorgonzola and many other cheeses is a fungus, too; this stuff is decomposing. That's what makes it tasty! That's also what makes it smell like feet sometimes. A friend in Strasbourg informs me that the French often store cheese in metal boxes at room temperature. The box has small holes in it: The holes are too small to allow flying insects to enter (maggots aren't noble enough), but they're big enough to let some air through. Foie gras isn't decayed, but it is made out of pathologically enlarged livers from some very unhappy waterfowl; veal is a similar deal. And how about thousand year eggs? Miso, shoyu? The list goes on.
Then there's all that murk and slop on Exile on Main Street by the Rolling Stones, and so many others: Scratchy vinyl, bootlegs, audience recordings. If Tom Waits' voice isn't afflicted with a noble rot of some kind, I'm damned if I know what is. So much good comes from the places where things begin to degrade in interesting ways. That's where the flavor comes from.