I was visiting a church in the Rioja region in Spain the weekend, and beside the organ keyboard, at the back of the church, there was a piece of furniture, like a cupboard, with a one meter disc of wood, standing vertically, and two loudspeaker on it. The disc could spin, and the loudspeakers were plugged through the axe, facing the main body of the church; I suppose the neutral wire was going through the other end of the axe.
So the loudspeakers are spinning, but always face the same direction.
Has anyone seen this before? Can someone explain what is the goal of this?