What a rich treasure trove this salute has proven already – and today’s continuation of TCM’s “Mad about Musicals” festival, June’s Tuesday and Thursday all-day marathon of movie musicals, contains several of the best. It’s a ridiculously rewarding tour, including Fred Astaire in three cinematic classics: 1951’s Royal Wedding at 10 a.m. ET, 1957’s Silk Stockings at noon ET, and 1953’s dizzyingly creative The Band Wagon at 2 p.m. ET. Then, in prime time, comes a double feature showing Gene Kelly putting his best feet forward: 1951’s brilliant Singin’ in the Rain at 8 p.m. ET (pictured), followed by the same year’s An American in Paris at 10 p.m. ET. That’s all in one day, all on one channel. In my day, it would have been an entire festival at a local revival cinema house…