The day's of projecting video live on stage to enhance the visual experience has come a long way, this Friday's performance of "Faust" at the Metropolitan Opera will see the most sophisticated interactive technology they've incorporated to date.

...Microphones (not the broadcasting kind) which are attached to the singers and positioned over the orchestra gauge volume and pitch. A system of infrared lights and cameras detect motion; similar technology is used to catch people trying to cross the United States border with Mexico, Mr. Lepage said.

A flock of digitally created birds swirls during Faust's opening aria. As Mr. Giordani's pitch changes, the birds change directions. As the volume surges, they swoop. When soldiers, supported by cables, march perpendicularly up the scaffolding on a projection of grass, the blades waver and part.

For the water-reflection scene, a high-definition camera captures the image of the moving boat. The software flips the image upside down, creates a shimmer and then instructs a projector to play it back simultaneously on the screen below the boat. The movements of ballet dancers during the "Menuet des follets" cause projected images of curtains to flutter and billow. In the production's most striking moment a JumboTron image of Ms. Graham's face appears behind her, emanating flames, as she sings "D'amour l'ardente flame."

New York Times via PSFK