May 4, or May the Fourth, has become the unofficial holiday of the “Star Wars” franchise. And to that end: Not a long time ago in a concert hall not far away, composer-conductor John Williams led the Chicago Symphony Orchestra in a program of his music, including “The Imperial March (Darth Vader’s Theme)” from “Star Wars: Episode VI — The Empire Strikes Back” (1983) performed in concerts April 26-28, 2018, in Orchestra Hall. May the Force, uh, Fourth, be with you!