Rhodes Chroma Polaris

I am wondering about what the mod lever on the polaris actually does.  it seems to engage the sweep (lfo) at the rate that the  sweep lever is set. but is its 'detination' [to use a modern term] the filter cutoff---or filter envelope? or what??   so then,  it adds the sweep rate to the filter--- at the 'level' set by the assignable control--- and how does this differ from the 'vibrato' that also seems to be adding this  LFO at this  single set rate?  I have other more modern synths that allow you to assign the mod wheel to many parameters--so im wondering what does this control do on the polaris in 'modern' terms .  I kinda wish it did more--or could be modded to have more or more intense  actions. it seems to have a fairly limited scope compared to my other synths.  any comments/ explainations?