The 1909 "The Count of Luxemburg" was by a composer whose best known and most successful operetta was what?
The Count of Luxemburg (1957 film):  It is based on the 1909 operetta "The Count of Luxemburg" by Franz Lehár. Franz Lehár:  He is mainly known for his operettas, of which the most successful and best known is "The Merry Widow" ("Die lustige Witwe").
i don't know