Fran,
I'm at home now. I will check this out tomorrow at my store. If I don't find the answer, I'll call someone at Roland and find out. My go to guy for Arranger products is out of the office until the end of the week but I should be able to find out.
If a midi file can have a track for vocal, lie the tune 1000 songs and the vocal harmonizer is responding, doesn't this mean that the harmonizer is being controlled via midi? Maybe I don't understand your full need here. Explain a little more if you don't mind.
George Kaye
Kaye's Music Scene
Reseda, California