Yamaha Japan has introduced the Vocaloid VKB-100 keyboard, a singing keytar thing based on their Vocaloid virtual vocalist technology.
The VKB-100 site is in Japanese and doesn’t have much information on it yet, but it looks like the keytar will allow you to play notes with one hand while articulating vocalization with the other.
The site does note:
The singing voice library of singer “VY 1” is loaded in “VKB – 100” beforehand. In addition, you can add singers up to 4 people (“Hatsune Miku” “Megpoid” “IA” “Yukari Yuzuki”) from a dedicated application for smartphones and tablets.
Here’s an unofficial demo:
Here’s an example of Vocaloid software in action, virtual vocalist Hatsune Miku ‘singing’ Coming Together: