so there is NO NEED to hook up midi in2 to jv1010 out. that doesn't help you out at all.
Unless he wants to recall the patch(es) or performance he setup for the song automatically. In other words, he can record the MIDI data "sysex" output from the JV -- in effect, it tells the JV which sounds, effects settings, etc. to use for the song the next time its loaded. This is a great use for the MPC, as you don't need to permanently save these parameters on the JV module, or dial them up manually, or even remember what user number you saved them to.