Accompanied by Saint-Saëns' "Samson et Dalila," workers rise from the understage to set up the world that is a stage. These men and women toil in shifts from 7 a.m. to 11 p.m. in the Vienna State Opera, sometimes making a thundering racket in the empty theater and then working as quietly as possible to avoid disturbing rehearsals or performances. They're vital to the operation ...