Deb

I like new ideas but this is on is way off. No audience is going to accept or understand someone behind a keyboard with a mystery voice coming out of no where. People focus on the vocals. They would think your faking the whole thing.
In the case of the demo the crowd was there to see the new instrument and what it could do, not a typical gig. Having a voice in the mix was just a nice extra thrown in to demo what the keyboard could do.
Look at the music shows on TV. They all feature vocalists unless there is an exceptional instrumentalist throw in, but rarely.