Read the following passage by Lena Chen, describing an orchestra rehearsing in a disused indoor swimming pool.

The pool had been empty for years, but its blue lane markings still ran along the floor beneath our chairs. Looking down from the gallery, our instruments must have appeared to be floating in shallow, invisible water. The conductor disliked that comparison. "It is a room," he reminded us. "Rooms can be measured."

That morning, everything was measured. Assistants placed strips of tape beneath each chair and adjusted the music stands until their edges formed straight rows. Cases were carried to the changing rooms. Bags were hidden behind a tiled wall. Even the conductor's pencil lay exactly parallel to his score. By the time we sat down, we had created a small republic of exactness in the deep end.

We began with silence. The conductor lifted one finger, and fifty people became still together. I could hear the electrical hum above the gallery and a single drop of water falling somewhere behind the walls. He waited until even these sounds seemed to belong to his count, then lowered his hand.

Our first chord did not leave us.

It struck the tiles, climbed the empty seating and returned from the glass roof. A thinner version came back from the changing rooms a moment later. The note we had finished continued travelling without us, dividing into pale copies of itself. Several players looked down at their music as if another instruction might have appeared there.

The conductor stopped us and began again. This time, we played more softly. The sound returned more softly too, but it still returned. Quick notes overtook slow echoes; rests filled with fragments of the previous phrase. The building seemed to be rehearsing an entirely different piece, always a few beats behind.

Then rain began tapping on the roof. At first it was a delicate accompaniment, a thousand fingertips keeping time on the glass. Within minutes, it became louder than the violins. Water drummed above us, the ventilation system coughed into life and a door slammed in the corridor. One of the cellists laughed. Someone else missed an entry. The conductor raised both arms, held them there and finally let them fall.

We stopped. The sound did not.

For several seconds, the last notes moved around the pool without players or conductor. The rain answered from above. A music stand trembled beside me, though nobody had touched it. All the straight rows and careful marks remained in place, but they no longer seemed to organise anything.

The conductor walked to the centre of the pool and listened. When he returned, he closed the metronome and drew a line through several instructions in his score. We started again, leaving longer spaces between phrases. Instead of fighting the echoes, we waited for them. The rain softened. Our notes crossed the pool, reached the roof and came back to us in the silence we had made.

At the end of the rehearsal, the final chord travelled away and slowly returned. This time, nobody turned a page or checked the score. We listened until it faded. What came back no longer sounded like a mistake. It sounded like an answer the room had been preparing all morning.