Vienna, Prague and Venice each have a concert trade aimed at visitors, separate from the season of the main opera house or philharmonic hall. A chamber ensemble or small orchestra plays a short programme of well-known pieces in a palace hall, church or historic salon. The repertoire follows the city: Mozart and Johann Strauss in Vienna, Mozart, Dvořák and Vivaldi in Prague, Vivaldi and Italian opera arias in Venice.
The link to each city is historical. Mozart lived in Vienna for the last ten years of his life and premiered Don Giovanni in Prague in 1787. Strauss wrote his waltzes for Viennese ballrooms. Vivaldi was born in Venice and taught at the Ospedale della Pietà. The concerts are built on that link. Some are played in period costume or on period instruments, and some add two singers or a pair of ballet dancers.
Expect 60 to 90 minutes. Longer programmes have an interval and church concerts often run straight through. Tickets are sold by seat category, usually three or four, priced by distance from the stage. Inside a category the seats may be numbered or free. Some tickets add a glass of sparkling wine, a dinner beforehand or a tour of the building. In Venice, one small opera format moves the audience from room to room of a palazzo, one act in each.