Opera? Though I am
NOT a "musical", I can understand that you are talking about the vocals at high notes with Vibrato. Talking about this opera feel, one tamil movie with that kind of effect that comes to my mind is Thevar magan. The vocals when periya thevar dies or Sakthivelu becomes official thevar magan - Different vocals combine with a violin (counterpoint this is?)...fabulous effect!!! In the instance where it is used for periya thevar death, it extends to "vaanam thottu ponaa song seamlessly..Epicness!
https://www.youtube.com/watch?v=XlknsKdwmJA
Btw, in Ai songs, ennodu nee song is the easy pick, sounds awesome in deed....others sound so-so so far...