Well, this is certainly a unique video. Youtube is full of people playing the guitar and singing, but as far as I know, this is the only video of someone playing guitar and singing while undergoing brain surgery.
The man's name is Anthony Kulkamp Dias and he's from Brazil. Exactly what prompted him to want to play guitar and song while undergoing brain surgery is anybody's guess, but that exactly what he wanted.Dias was kept conscious during the procedure and he performed for the doctors and nurses in the ER while his brain was being probed.According to the doctors, Dias played "Yesterday" by the Beatles, he also performed some Brazilian folk songs and even threw in a song that he had written for his son.

Dias did all this performing while doctors spent six hours operating on him for a tumor. By the way, the staff says that 90% of the tumor was removed and Dias is expected to go home in a few days.

He must have done a pretty good job of playing since Dias reports that he even performed an encore for the medical staff.

Here's a video clip of the operation featuring Dias singing "Yesterday."