What's even more fascinating to me is that the Köln Concert is just one of many long-form improvisations he did and, arguably, far from the best one.

In roughly the following order, I recommend:

Paris, 1988

Vienna, 1991

Lausanne, 1973

Sun Bear Concerts, 1976 (5(!) concerts in 14 days)

Bremen, 1973

La Scala, 1995

Munich, 1982

...and so on.

If you _get_ Jarrett, it's a love affair for life.