Bungee-jumping, lip-syncing Rhinemaidens soar across the Lyric Opera of Chicago stage for “Das Rheingold.” The NY Times looks behind the scenes at the aerial mechanics of keeping three gymnasts gracefully afloat for an underwater appearance. It’s essentially a circus act set to a Wagner score with a choreographer who has worked with Cirque du Soleil. Next up, in “Die Walküre,” the (in)famous Valkyries leap across stage with the help of four trampolines. No word on whether Brunhilde later launches herself into the funeral pyre with the aid of gymnastics equipment.