Plot: Fred Astaire is Michael Feinstein’s favorite singer—but he also was the favorite singer of Irving Berlin, Cole Porter and the Gershwins. Why was this dancer, first-and-foremost, so beloved by the America’s great composers? With that question Feinstein launches into an exploration of the marriage between music and choreography, unearthing rare home movies of Astaire rehearsing on set, and some remarkable memorabilia from that other screen-dance icon, Gene Kelly