The Köln Concert
en.wikipedia.org
en.wikipedia.org
The story behind the album is worth reading about: 11:30 PM start time, broken piano, tired pianist who almost bailed, sold-out show, etc. The entire piece is improvised and Jarrett starts by playing the same melody that the opera house played to let people know to take their seats.
You can listen here: https://www.youtube.com/watch?v=Pd_Kti6jvy8&list=OLAK5uy_lap...