Gioachino Rossini retired from opera in 1829, but decades later his creativity erupted in a dizzying array of chamber works he called “sins of old age.” These miniatures, by turns deliciously lyrical, hauntingly spiritual, and raucously funny, serve as a showcase for Caramoor’s Bel Canto Young Artists led by Derrick Goff, and as a perfect amuse-bouche for those planning to hear Aureliano in Palmira.