Surgeons had to perform an awake craniotomy to remove the tumor from the brain of Ambrož Bajec-Lapajne.
To ensure Ambrož’s cognitive functions were working properly, he was encouraged to talk throughout the surgery, and was even asked to sing while surgeons were working on his exposed brain, Metro reported.
The neuro-surgery team in Utrecht, Holland asked Ambrož to sing along to Schubert's "Gute Nacht" in two different keys – major and minor – so doctors could monitor his ability to sing and recognize the key change.
The operation was successful, with Ambrož saying: "It's been more than a year since and I’m doing fine, continuing my professional singing career."