Read the following extract from an account by Joel Mercer, who observes the restoration of an organ in an old concert hall.

For most of the winter, the organ remained silent behind a wall of scaffolding. From the floor of the empty hall, its pipes rose above the dust sheets in ordered ranks, some no thicker than walking sticks and others broad enough to hide a person. Even covered, they gave the stage the severe appearance of a guarded palace. Yet each morning the restorers climbed towards them carrying brushes, scraps of felt and little trays of screws.

On the day of the first test, I followed the chief restorer through a narrow door beneath the keyboard. The public face of the instrument vanished. Behind it stood timber frames, ladders, cables and pipes crossing in every direction. Small labels had been tied to hundreds of parts. Some were written in faded ink; others were new and sharply white. The organ, which had seemed from the hall to be a single grand object, had become a crowded collection of separate pieces waiting to agree with one another.

The restorer showed me a strip of leather taken from one of the bellows. It lay across his palm like the skin shed by a small animal. A crack ran almost from one edge to the other. 'That was enough to silence twelve pipes,' he said. He replaced it with a new strip, smoothing the join with his thumb, then asked everyone in the building to stop work.

At first, the electric blower produced only a low shudder beneath the floor. Air moved into the instrument with a sound like somebody drawing a long, cautious breath. One wooden panel trembled. Somewhere above us, a valve clicked and clicked again. The restorer listened with his head tilted, not towards the largest pipes but towards the faint mechanical whisper behind them.

He sat at the keyboard and pressed a chord. The answer did not seem to come from his hands. It arrived from the walls, the ceiling and the floor at once. Dust stirred along the balcony rail. The empty chairs appeared to vibrate in their rows. The sound was not merely loud; it occupied the hall so completely that the room seemed to have become part of the instrument. He added lower notes, and the air pushed against my coat.

Then one high note began to waver. It thinned, recovered and thinned again, a bright thread repeatedly pulled almost to breaking point. The restorer released the keys. The enormous sound vanished so quickly that I heard a screw roll across the stage. He climbed back inside the casing and found a felt pad sitting a few millimetres out of place.

When he returned to the keyboard, he tested only that single note. It rose cleanly into the hall, narrow but steady. Nobody spoke until it had faded. Above us, the pipes still resembled a silver regiment, but I could no longer see them as remote or unshakeable. Their authority rested on air, leather, felt and the accuracy of a person's fingertips.