For me, it would have to be something nice, but not so interesting that I want to stay awake (Ariadne auf Naxos). Or something I’ve heard a million times (The Magic Flute).
Beethoven has always been calming for me, so maybe Fidelio too.
If you’re looking for beautiful music, maybe Tosca or Rusalka.
There are others that I wouldn’t necessarily fall asleep to, like Don Carlo, Pagliacci, Rigoletto, or La Traviata. This is a pretty good list of some of the best known operas.
Yeah. Those keys on the piano are E and F. You can see those notes in the sheet music for the title track. Those long rows of notes are a bunch of E’s and F’s.
If you hit the play button in the bottom left corner, you can hear a computer-generated version of the song. Real version here.