“[David Hertzberg’s] The Rose Elf features a pair of star-crossed lovers who are figuratively torn apart when one of them is literally torn apart by a jealous rival. … Opera-goers will follow a candle-lit pathway through [Green-Wood Cemetery] to the subterranean tombs, and take seats along one wall of the catacomb’s long, narrow hallway, with the performance taking place all along the crypt-lined corridor.”