You're listening to a special archive presentation of TED Talks Audio.

This talk features economist, journalist, and broadcaster Tim Harford, recorded live at TED Global London, 2015.

Late in January 1975, a 17-year-old German girl called Vera Branders walked out onto the stage of the Cologne Opera House.

The auditorium was empty.

It was lit only by the dim green glow of the emergency exit sign.

This was the most exciting day of Vera's life.

She was the youngest concert promoter in Germany,

and she had persuaded the Cologne Opera House to host a late-night concert of jazz

from the American musician Keith Jarrett.

Fourteen hundred people were coming,

and in just a few hours, Jarrett would walk out on the same stage.

He'd sit down at the piano and without rehearsal or sheet music, he'd begin to play.

But right now, Vera was introducing Keith to the piano in question,

and it wasn't going well.

So Jarrett looked at the instrument a little warily,

played a few notes, walked around it, played a few more notes,

muttered something to his producer,

and the producer came over to Vera and said,

if you don't get a new piano,

Keith can't play.

There'd been a mistake.

The opera house had provided the wrong instrument.

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