One is an adaptation of a well-known effect called "optical tweezers" in which objects can be trapped in the focus of one or two laser beams.

BBC: Nasa examines 'tractor beams' for sample gathering

May stressed the new "effect" was not a hologram, calling it "an optical illusion of sorts".

BBC: Freddie Mercury

An optical laser reads the transparency and creates a wobbly, out-of-tune, almost eerie-sounding keyboard effect.

NPR: Marco Benevento: Jazz Not Jazz