gather
輳 centers on things coming together into one place: gathering, converging, or assembling, often with a sense of spokes meeting at a hub.
輳 combines 車 (vehicle, wheel) with 奏, which likely contributes the sound and the idea of bringing together, as in spokes converging at a hub.
A vehicle 車 gathers its parts together like spokes meeting at a hub; the right side 奏 suggests a performance where everything comes together in harmony.
For ソウ, imagine all the parts gathering to form a single soul of the machine: soul -> ソウ, and the vehicle's components converge into one working whole.