Kind of, sort of on topic
We went to Salzburg, Prague and Vienna in late may, early june.
Took a tour of the Vienna opera house, its a cool place. Didn't see an opera there though. They do show operas on a big screen in front of the building, and put out a hand full of chairs for people to watch. They also see standing tickets, but I didn't feel like standing for an entire opera lol.
In Salzburg we took a tour of the place where they filmed the music festival in the Sound of Music. They have a few theaters there for music, maybe even operas.
Also saw Mozart's birthplace in Salzburg, and the Mozart museum (at one of his residences) in Vienna, the one in Vienna was nicer, more to see and more interesting.
Prague was very crowded, but I still enjoyed it a lot. But in August its likely to be even more crowded, and hot, so be prepared. They also don't speak as much English in Prague as western European countries, at least that was my experience. But we managed fine. Google translate helps.
Enjoy your trip.
Many years ago, I saw the Sydney Opera house, but also didn't see an opera there. Very cool building.
