Essentially, you will connect the 9-9in MIDI output connector of the keyboard to the 9-pin MIDI input of the vocal processor. The audio output of the vocal processor will connect either to the auxiliary, audio input of the keyboard (if the S-750 has one) or directly to any audio input of your PA system. Then it's just a matter of setting up the midi channel to control the system, which I believe is Keyboard and Style and channel 3, but I'm not positive about this part on the S-750.

It will go out this afternoon, along with an instruction manual.

Good luck,

Gary