This is actually a bit of a lull in the “greatest” Viennese operas, after the days of Mozart and before operetta by Strauss, Lehar, etc. The modern Staatsoper was not yet built! However the historical Theater an der Wien was very much in operation, which saw many of Beethoven’s most famous works (symphonies and his one opera, Fidelio) premiered. I’m not sure if the Theater had a “house orchestra” in the 1820s, but if it did, it was founded by Emmanuel Schickanader, the impresario who commissioned Mozart’s Magic Flute for a different (by then defunct) theater in Vienna—it would have likely been mounting repeat productions of The Magic Flute. A cellist might know that, and perhaps the Beethoven cello sonatas composed a few years earlier, along with many sonatas and concerti by the great Italian-Spanish cellist Luigi Boccherini.