Melodyne isn't even a realtime process on the fastest computers you can buy nowadays... Plus, I'm sorry, but despite the impressive demos, it is still no magic bullet to change anything into anything else. You'll notice the demos use VERY clean, very simple sounds as sources. Feed it something more complex, and it has a hard time.

We've got several generations of computers and audio hardware to go through before this is even possible on a TOTL mutiprocessor computer. So that would mean another five or ten years before an arranger gets anywhere NEAR that power on board!

Dream on...