The centennial of George Gershwin’s Rhapsody in Blue continued into its fourth quarter with The Knights’ latest at Carnegie’s Zankel Hall, featuring a world premiere as part of their multi-season Rhapsody-themed commissioning project. The Brooklyn-based orchestra welcomed pianist Aaron Diehl for a unique take on Gershwin’s familiar piece for piano and orchestra, a new composition for the same combination by Michael Schachter, balanced, in a stroke of programming ingenuity, with Beethoven’s Fourth Symphony.