Denyce Graves, Stephanie Blythe, Robert Orth, Carl Tanner and Matt Boehler are just some of the Wolf Trap Opera Company alumni who will return for a 40th anniversary concert dubbed "Opera's Greatest Hits." Stephen Lord conducts the stars and a 70-piece orchestra in performances of signature arias by Verdi, Puccini, Wagner, Donizetti, Rossini and more. Wednesday, Aug. 24, at 8 p.m. Wolf Trap, 1645 Trap Road, Vienna. Tickets are $20 to $55. Call 703-255-1900 or visit wolftrap.org.