A good question…
Like on the Buchla 204 “Quad Spatial Director”, there would be four mono ins: 1, 2, 3, 4, and one quad out: Front Left, Front Right, Rear Left and Rear Right. Each of the four mono input signals could be panned around to any of the four channels, which I’m imagining would be around the four corners of the room. All four mono ins would be mixed into the same quad output, but each input could be panned to its own location in the room, as desired, using the joysticks.
Stereo signals could be patched into two adjacent mono inputs. In basic usage the two adjoining joysticks could be manually swung to the desired positions, which could be separated by any amount, as directed by the joysticks. The stereo inputs can be near each other in a corner of the room, or on opposite walls. They can pan together, or one channel can race ahead of the other, spinning more rapidly, or it could go in the opposite direction. One channel could sit in the middle of the room while the other bops back and forth, randomly, between the various corners.
Each signal is completely separately controlled, but the controls can be linked by similar hand movements.
(slightly edited for clarity)