This is simply incredible.

Slovenian opera singer Ambrož Bajec-Lapajne performed while he underwent brain surgery in June of last year after he was diagnosed with a tumor. He sang Franz Schubert's "Gute Nacht" during the operation.

Doctors wanted Bajec-Lapajne to sing because, as the Washington Post explains:

...so that they can speak or perform other high-level functions as surgeons work on them. They're giving doctors a map to work with when it comes time to remove the actual tumor....In Bajec-Lapajne's case, doctors wanted to monitor his ability to recognize changes in key, since that's something he relies heavily on for his profession.

There's a frightening moment at the 2:45 mark when he couldn't speak, but, after some reassuring words from one of the doctors, he managed to bounce back slightly more than a minute later.

It's pretty riveting -- it's not every day you see brain surgery being performed, let alone being performed with the patient awake and singing.

Consider the procedure a success, too. Bajec-Lapajne says he has continued singing professionally and he's"doing fine."

Having patients perform in some capacity during brain surgery seems to be a trend of sorts. Earlier this year, video surfaced of another man playing the Beatles on guitar while he was under the knife.