First of all, what do we mean by “low key photography”? One definition, courtesy of Wikipedia:
Low-key photography is a genre of photography consisting of shooting dark-coloured scenes, and emphasizing natural or artificial light only on specific areas in the frame.
The old camera photo was taken in the office, not that dark, but with careful use of off-camera flash (two flash units in this case), it’s possible to create the dark environment. The office has white walls, one of the tables used is white and light bounces off the white ceiling too. So, as can be seen from the setup shot below, a black cloth was used (over a box to give some height), a black reflector (yes, black to absorb rather than reflect light) and the camera on a tripod with the two flash units on manual. A little bit of editing and voila, a low key image.