As a decent singer but very poor musician, I've been watching developments in this sort of technology for a while, and have never seen anything so close to the holy grail as this... Check this demonstration out -- the performance proper starts at 1:50

https://www.youtube.com/watch?v=C-pCfHxbxp8#t=128

He's doing a Kickstarter campaign lasting a few more days ... more details here

https://www.kickstarter.com/projects/evanbalster/imitone-mind-to-melody

Pretty mindblowing, I'd say!

(I'm unaffiliated by the way)