Haha... I loathe those public pianos. But if one is gonna do it, the easiest thing to do is just some chords with rhythm of a very popular song to sing along to, like Life on Mars or something.
When people start doing Beethoven or Debussy I just see them as narcissists trying to go viral on tiktok XD
I was just trying to entertain my sister in law, and turns out... the native wildlife too.