I have the original version of SONiVOX's Vocalizer and it did a really good job on any audio source you fed into it. They now have version 1.1 and advertise it with:
"Vocalizer Pro 1.1 is a totally unique MIDI controlled effect processor that can transform any audio track, any audio source, or the output from any VI in your DAW host into an unbelievably lush, musical, performance instrument. It’s unlike anything you’ve ever heard.
Part instrument, part processor, Vocalizer Pro 1.1 is the ultimate instrument expansion tool. Offering endless sound-sculpting possibilities, Vocalizer Pro 1.1 is ready to harmonize, modify, fortify, enhance, and re-synthesize any instrument—or any sound—in ways you never thought possible. Two rows of MIDI-mappable pads provide unbelievable performance control."
http://sonivoxmi.com/products/details/vocalizer-pro