I don’t know whether this has been mentioned before but…
use the square output of the LFO section of the VX-351 and connect it to the attenuator. Send the output of the attenuator to modulate the pan on the respective input at the back of the Voyager.
Do you hear any clicks, no matter how much attenuated the signal is?
Normal behavior. That is the VCA’s opening and closing so quickly. If the VCA’s were of a poorer design you would not hear it. To avoid it, run the sq through a lag processor first. (Or, if you don’t have one, build a patch cable with a capacitor from signal to ground to delay the rise and fall time of the sq wave. Or use the triangle wave from the LFO.)
The VCAs can be driven at audio frequency for some really harsh distortion like output.