Question: The 1909 "The Count of Luxemburg" was by a composer whose best known and most successful operetta was what?
Sentence (from "Johann Strauss III"): His talents were not fully realised during his lifetime as musical tastes had changed in the Silver Age with more popular composers such as Franz Lehár and Oscar Straus dominating the Viennese musical scene with their operettas, although his uncle, Johann Strauss II, supervised his development as a musician, a fact disputed by Eduard Strauss.
Relevant evidence: No