All the commands for voice changes have to be made from the controller. I haven't done this since I used the Midjay, but as I recall you have to look up the command strings for the various voices and assign them to the locations you wish on the controller. I had something like 50 voices assigned on the MJ.
When I get my BK back, I'll be able to help more, but you'll probably have it figured out by then.
Don