Rehearsals are underway for “Million Dollar Quartet,” Mill Mountain Theatre’s first post-pandemic show, which opens July 28. The musical is based on a real 1956 incident, when Elvis Presley, Jerry Lee Lewis, Carl Perkins and Johnny Cash held an impromptu jam session in a Memphis recording studio. (From left) Seth Davis, resident music director at Mill Mountain Theatre; Brady Wease as Lewis; Michael Perrie Jr. as Perkins; Edward LaCardo as Presley, center; Ross Neal as Brother Jay; and Tyler Breeding as Cash. Wease, Perrie and Neal appear in the show courtesy of Actor’s Equity Association. See Arts & Extras, Page A2.