happyOOTer,
Rov Soloveitchik matired all classical music, including opera, as not falling under the kol isha prohibition. I’ve discussed this at length with my rabbi, a talmid of The Rov, who actually attended an opera himself for the first time last spring (at the age of 70!). That this was intended not as a theoretical statement but practical halachah le-maaseh is that Yeshiva University has been holding an opera fundraiser for decades. This year it was Puccini’s “Turandot”.
If your rabbi holds like The Rov, do try to see Verdi’s Nabucco. It is a very moving opera with a happier ending than what happened in real life.