Another APRO issue (Maybe)

Hi,
 
 I have been discussing this in the hardware forum, but as there is very little footfall there I decided to elevate it to here.
 
How the heck do you get the Upper/Lower/Split/Dual buttons to work.  We have been assigning the sounds as per the manual using programs on different soft synths ie Upper > Z3ta2 Progra, Lower > Psyn Program, but nothing changes on pressing the buttons ie if Im playing using Z3ta2 then press the lower button the souund still stays the same instead of changing to the Psyn sound.  I can see the program change in the LCD display but the sounds dont.  I have also tried this using the same soft synth with the same result.
 
Am I missing something here? The manual makes it sound simple enough.  I know that the other forum member is trying to play two sounds concurrently with a split keyboard with the same success.
 
Any thoughts guys and gals? Have I totally missed the point?
 
 

Thanks Karl ever dependable :-)

I'll try later, but why the hell doesn't the blinking manual say that!!!

To me the APRO manual is written in swahilli! Utter gibberish! 

Thank god for helpful forum members. :-) 

Ok I now have my headround it thanks Karl!

All makes sense now, basically to use those functions the synth in question needs to be multi-timbral. I've tried it with TTS-1 and all works as (un)advertised in the manual.  I now need to see if I can maximise its usefulness.