Well, those cycle writers from yore must have thought of such things as a Sturmey TF or ASC when they wrote about "single speed fixed", opposite would be "two / three speed fixed".
Besides, there also were back pedalling brake hubs with two, three, four or even five speed derailleurs, like the German Renntorpedo.
Hoping to have complicated things,
Toni Theilmeier, Belm, Germany.