THE GENUS Broadway operetta, as distinct from the nineteenth-century comic opera, had two major influences: Victor Herbert and the Viennese operettas of the Silver Era. Sigmund Romberg and Rudolf Friml were the leading composers of the late teens and 1920s, and both had middle-European backgrounds. Though much of their work in the teens was frankly, requisitely imitative of Herbert, their operettas of the '20s were as spectacularly romantic as the gushing costume operettas of Lehár, if not more so. The uniformed male choruses that Herbert had held over from the older comic operas were retained by Friml and Romberg, and given similarly stirring marches. Perhaps influenced by the close-up intimacy and spectacular passion of the hugely popular silent screen, operettas were forced to be increasingly romantic and full-blooded, rather than satiric or comic.
What is astounding about the '20s is that while these hot-blooded romantic operettas were being created and consumed, the same years saw the birth of the fast, dancing, jazz musical comedies of Gershwin, Youmans, and other composers, as well as excellent revues, both spectacular and intimate, and also attempts to modernize operetta into something almost as zippy as musical comedy. It was truly the Golden Age of the American musical theatre, and one that did not really end in 1929. The potent romantic and sentimental elements that had made The Student Prince and Show Boat such superb operettas were simply streamlined in the 1940s and transformed into the "musical play, " a euphemism for romantic operetta. The main differences between the 1920s and the 1940s operetta involved the replacement of passion with compassion and psychology, cleverer segues into songs that had to do more sophisticatedly with character and plot than before, an attempt to use the comedian and soubrette more effectively in the story, and, most importantly, the use of ballet for story or mood