As the proverbial saying goes: "Necessity is the mother of invention." It was, frankly, a matter of economic necessity that led a 36-year-old Austrian conductor named Clemens Krauss to program an all-Johann Strauss concert by the Vienna Philharmonic at the Salzburg Music Festival on today's date in 1929. The Salzburg Festival was established in 1920 with high ideals but insecure funding. Its mission was to offer world-class performances of theater and music, old and new, programmed to reflect Austria's unique mix of cosmopolitan European values and parochial Catholic traditions. To succeed, the Festival needed both strong local support and wealthy visitors from abroad. Sometimes it worked, sometimes it didn't, but in 1929, as the Festival approached its 10th anniversary, its finances and future seemed uncertain. Now, Krauss knew that Strauss waltzes were popular with both the natives and the Festival's international visitors, so why not offer a whole concert program consisting of nothing but the dance music of Johann Strauss? The August 11, 1929, concert proved to be a resounding success, and the idea was repeated at the Festival several times over the next decade. Back home in Vienna, Krauss again revived the idea of an all-Strauss concert on December 31, 1939, this time to boost wartime morale, not box office. That year-end tradition continues to this day, as the Philharmonic presents its annual New Year's Concert, broadcast worldwide from Golden Hall of the Musikverein in Vienna.