Thanks to Sean and Vasco for sending me a link to this article: "Keith Jarrett gets career Golden Lion".

"US jazz pianist Keith Jarrett has been given the Venice Biennale Golden Lion for career achievement. The American pianist and composer will receive the award at the 62nd Biennale Festival of Contemporary Music on September 29.

[...]

For this occasion, Keith Jarrett will perform one of his legendary improvisations on the piano, unique and unrepeatable events that have punctuated his career and contributed to redefining composition for the piano."

It's not completely clear from the article whether Keith will play a full-length concert or whether he will only play at the award ceremony.