I've been dicking around with a Eventide PitchFactor Harmonizer this week. The interface would intimidate a Yamaha DX programmer. The manual is about 100 pages and you really must read it to understand this nasty little box of pain.
On the bright side, the thing shifts pitch and maintains instrument timbre / modulation. (and a load of other useful pitch / delay stuff). I want to use it with Moog and wind synth. It works well with Mellotron input. I'll post a demo recording soon.
The Eventide people tried to jam all sorts of strange things into one little box. I'm sure it has lots of potential but it's going to take months of farting around to figure it out.
http://www.eventide .com/AudioDivisi on.aspx