Neat!

I still think that playing violin and singing at the same time would be harder (as long as you're not singing the same melody you're playing, of course). With cups and hands they don't have to worry about intonation, only rhythm - which is hard enough, agreed. With violin+voice, it's like when you play double stops : both notes must be absolutely in tune for it to sound right. And it's hard to think about two different notes (of two different melodies) at the same time, one to play and one to sing. For me, it feels like I need two brains... it would be like :

1) thinking about what note I'll play next, and placing the left hand finger at the right place ;
2) then thinking about what note I'll sing, and singing it while drawing the bow.
Long sustained violin notes offer a reprieve during which it's easy to sing anything you wish.