I was tuning a piano the size of a cathedral

I'm tuning a piano that fills a cathedral, but the customer is the building itself and I'm walking up the strings like scaffolding. The tuning hammer is missing, so I'm using my knuckles to tap each pin, and the weird part is the sound keeps folding back into itself, like a Möbius curve of resonance. I keep telling the stone ears that the A will only hold if they let the whole room breathe, and somehow I understand the hammer was never the point.