The National Virtual Medical Orchestra plays “Nessun Dorma” by Giacomo Puccini, sung by Tracey Welborn, registered nurse and tenor. The orchestra performs its Christmas concert December 17, presented by Carnegie Hall. Tracey Welborn, RN, did not expect he’d be singing “Nessun Dorma” — the well-known aria from Puccini’s opera Turandot — with a national orchestra made…