Emu XL-7 & MP-7 User's Group

Hi to all,

I've got a MP7 ... here is configuration :
IN : Master Keyboard
OUT A : nothing ...
OUT B :
ACCESS - VIRUS (ch1/2/3)
YAMAHA - TX81Z (ch4)
TC - Mone (ch5)
ROLAND - RSP550 (ch6)
YAMAHA - 01V (ch7)

I can command my virus for example by playing on my master keyboard 
by selecting CH1B but i can't find how to change the sound !!! not by 
selecting a preset, can't send a program change ... don't understand !

The Same for all devices connected to OUT B.

Is this possible ??? How to arp an external module on OUT B ???

IS IT ALL BECAUSE IT'S OUT B ???

Thanks ...