The afternoon concert sounds its last notes from pipes high above the ground floor of the grand court of Macy's in Philadelphia, home to the world's largest playing pipe organ.  Shoppers suddenly aware of a change pause and applaud the performance before returning their attention to sales racks and shoe displays.

Scott Kip, artist and restoration woodworker for the nonprofit Friends of the Wanamaker Organ, led me through the ladies casual wear section to an unmarked door and service elevator. Kip maintains a woodshop inside Macy's where he repairs and rebuilds parts for the century-old organ.

On top of a cat walk five floors up from the grand court and behind the organ's facade, the bass pipes rumble my tripod. The organ is almost entirely made of wood.

It feels cozy inside. After a few hours of crawling through passages and up ladders, I feel as if I am traveling in a wooden submarine. Wind channels hiss around my camera. The giant bellows expand for another performance.

Since its installation in 1910-11, the organ's parts have been replicated and replaced by a long line of craftsmen keeping the organ playing of which Scott Kip is the latest.