An "opera concert" in Palais Palffy. A Viennese orchestra performed a one hour concert, 16 songs, with the most famous works of Mozart and Strauss (the sounds of Vienna's cultural heritage). The orchestra was accompanied by two opera singers and two dancers. The tickets also give you acces to the city library.
Honestly, I liked the performance but the hall itself looked like the city hall of a local town. The orchestra was performing on a stage but the singers and dancers weren't on a platform. They were sometimes hard to watch.
We bought tickets on the streets near the real opera but you can probably find them online too.