Fifty years ago, acclaimed jazz pianist Keith Jarrett sat down at a worn-down practice piano that was mistakenly brought to the Cologne Opera House stage to play a concert of improvised music for more ...

Keith Jarrett improvised the best-selling solo piano performance of all time, and so did the 18-year-old girl who scrambled to put the show together.

For a lot of years, Vera Brandes couldn’t listen. Not once had she heard the bestselling solo jazz album of all time—Keith Jarrett’s passionate and sublime The Köln Concert—though she’d been essential ...