He performed this in 1970 with one day's notice, because Michelangeli cancelled his appearance.
The last time he performed it was in 1966, to record with Stokowski.  Gould's music memory is just phenomenal. As a matter of fact, he could recite multiplcation table for 3-4 digits. His extraodinary memory plus his odd behavior led people think he suffered from Asperger syndrome that is related to autism.