The other day I did these actually blindfolded, rather than just in a dark room or with my eyes closed. It makes a difference because I can no longer open my eyes to cheat, and I get the full effect of depriving myself of that one sense. Playing the piano is not a mostly visual proposition. We think it is because we need to read sheet music. That is fine for learning but not essential for playing. We also think we need to see where the key are. Maybe so, but the hand should know this, just as when I'm typing now I am not looking at the keyboard at all.
If I hit a wrong note I should also know what note it is, and decide whether I have played an E instead of an F, for example. My ears should tell me this.
I should also be able to hear the notes before I play them and sing along in real time to my playing. Surprisingly, I can do this. The ears can be trained even for an old guy.
Then I started playing other tunes to the chords of I got rhythm, seeing whether they fit or not, the 1,6,2,5 of Blue Moon at the beginning for example, which also seemed to work with "These Foolish Things."
I saw a movie the other night, Mr. Church, in which the "magical negro" part is played by Eddie Murphy. It is interesting that jazz is used as the metonymy corresponding to the "magical negro" trope. The character mostly plays in the style of the 1920s or early 30s. This makes sense because making him a bebop player would be not safe enough for a character who is supposed to represent the dignity expected out of this character, even though the movie itself takes place in the 1970s and 80s! Of course I object to almost any treatment of jazz in a movie. I can't help it.