Does it bend?
Though it lacked the pitch bend wheel that its bigger brother, the Jupiter-8 would later sport, the original Jupiter-4 included a small joystick bender control on a horizontal axis that allowed some rather rigid control of VCO pitch, VCF cutoff, VCA volume or how much LFO modification is applied to the VCO, VCF or the VCA.
The Mercury-4 now allows your MIDI controller’s pitch bend wheel to serve the same function, albeit more fluidly and in a more performance-ready way. It’s nice to be able to jiggle around modifiers like this, developing evolving textures as modulation is introduced and removed musically.
Couple this with the velocitysensitive MPE support and the Mercury-4 offers a radically different experience than the one offered by the hardware’s original capabilities.