Thanks Trax and Noel. That's good to know. I don't like Harmony Engine well enough to buy it anyway. The interface takes up the whole screen, I don't like the layout, and I haven't figured out how to get it to do anything other than play as an effect insert in RB. The voices are decent if you start with a really clean track. I can see where it could be quite flexible for someone into vocal arranging with the right DAW, the patience to diddle with it and of course trust the company.

I'm going to try the Mu Voice. They have a great demo on youtube so I'm curious.