the tricky thing is that is he really sentient or is it all just a matter of programming. Take away a few lines of code and he can no longer sing. Take away a few lines of code and he can't speak, take away a few lines of code and his whole personality is changed
A rather philosophical question! I mean, ultimately how do you know anyone is truly sentient and not just a clever simulation?
The Doctor certainly passes the Turing test. And, well, you can probably change a human's personality or eliminate their ability to sing if you zapped the right part of the brain.