I think it’s a figurative usage as a reminder of blood, but not for sure. Why is the word Hungarian used here?
(He is a professional pianist who holds lessons open to the public.)
When I told him that one of the students had likened it to an energy radiating from his hands into theirs, he laughed and offered his own image: “I give them a blood transfusion right there on stage! After all, I’m Hungarian.” (The Piano Shop on the Left Bank by Thad Carhart)