How many people fall asleep at operas? A lot, and even if that weren't the case, I always did. Not because it was boring, but its so relaxing and echo-y and resonant.
I've fallen asleep during the third act extended fight scene of the last 5 Marvel movies I've been too that weren't Deadpool. Same vibes. But, I still wouldn't use them to try to sleep.
But if you're looking for relaxing, echo-y, and resonant check out Brian Eno's ambient stuff. Start with "Music for Airports" and go on from there to some of the others if you like it.
If you're stuck on opera, maybe you'll have interesting dreams trying to fall asleep to The Magic Flute. I'd probably just get the tunes stuck in my head.
Also, the genre of modal jazz is rather slower and more resonant than its more hip and excitable cousins. Might be worth exploring. Syncopation would keep my mind to active though.
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.
Well, we would have to know which country you hail from in order to know what constitutes a foreign language to you.
Anything not english and probably not French haha. I want to not understand it at all, anything Latin-derived might be decipherable now that I think about it ;)
Happy cake day
I like lighthearted ones such as the Barber of Seville or "Zar und Zimmermann". If you want more oomph, The flying Dutchman is a great choice. I also like Carmen and Nabucco for some really catchy melodies and the magic flute is nice too. Depending on what language(s) you speak, some of those will obviously not be foreign, sorry :-D