Stereoscopy is a technique used to give an illusion of depth in an image. Sir Charles Wheatstone invented the earliest type of stereoscope in 1838 - it could be argued that stereographs were the original virtual reality.
Human vision combines two perspectives (what the right eye sees and what the left eye sees) to give brain information different perspectives. The difference in what the eye sees is called parallax. In virtual reality, cameras used for to filming are also separated into left and right cameras to create a perfect parallax effect.
"Duets" is a meditation on the idea of new media - technologies that we claim to be "new" often have their roots in technologies that are sometimes as much as one hundred years old.