Have mapped a MULTI INSTRUMENT but LOGIC will NOT play different voices from the MIDI instrument even though each track is on a different MIDI channel....PLEASE HELP!!

I have connected my YAMAHA MOTIF8 to LOGIC EXPRESS MIDI in and out cables - I have set up the DEFINE CUSTOM BANK MESSAGES in Logic Express - I have done everything I can think of --- but STILL CANNOT here "DIFFERENT" voices out of the MIDI instrument even though the LOGIC EXPRESS TRACKS ARE set to DIFFERENT MIDI CHANNELS in the INSPECTOR.

Even though I have each track set on DIFFERENT MIDI CHANNELS only one voice from the synthesizer plays through LOGIC - it is the last voice/track selected in LOGIC. VERY FRUSTRATING. Is it possible that LOGIC can only play one voice at a time on the synthesizer? That does not makes sense - then why would there be 16 subchannels on the MULTI INSTRUMENT in the ENVIRONMENT Window. PLEASE HELP!!!! I'm stuck.