Come one, come all, and celebrate “the beauty, excitement, and diversity of Carnegie Hall past and present.” The main event online is absolutely free to viewers around the world. Pricey extras for fat cats include “a private virtual performance with a premier artist,” for instance, or “a private virtual cocktail reception with a young artist from a Carnegie Hall program.” Mercedes T. Bass and Hope and Robert F. Smith share the marquee as gala lead chairmen, with Roy Weathers of PricewaterhouseCoopers LLP onboard as corporate chairman. What’s the program?, you ask. So far, mum’s the word. —M.G.