Wondering what happened after 2:43mins?
That was Ambroz Bajec-Lapajne, the Slovenian opera singer performing Schubert’s ‘Gute Nacht’ during surgery.

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In Brain Mapping, the Neurosurgeon electro-stimulated the area controlling movement of muscles used for speech. Then during tumour resection, he avoided that area. Tumour removal near this functional area can produce this too.