"All week, a man with a microphone has walked the subway platforms to collect the clattering of the rivets and the whistling horns, the distortion in the loudspeaker, the hush in the compressor’s song and the dying of the brake like some wounded thing.

Even in that racket, some find value. The recordings are the chief selling point of a new reproduction of a subway train by the Lionel model train company made under a license from the Metropolitan Transportation Authority for completion by year’s end.

. . .

Then the men emerged from the tunnels with their gearboxes and their tripods to walk the Brooklyn sidewalk like some sonic spelunkers from an alien world, bound for another station, another yard, another car and the sound of a hundred tongues talking and the quack and the hum and the clack and the thud calling one to another while the trains go by.

Outside a railyard near the Green-Wood Cemetery, the party was stopped by a security detail, held up for an hour to wait by a razor-wire fence.

A cellphone rang and Mr. Koball answered.

“Neil!” he said. Then he paced by the tracks for a good long piece, speaking of switches and routers and circuits, happy as a schoolboy. By and by he passed the phone along, and the familiar voice on the line grasped at the grandeur of the city trains.

“It’s a symphony of motion and sound,” Mr. Young said. “New York City. What’s more American than that?”