The former Rennes striker has arrived as the club's record transfer.
"When Asamoah signed in the boardroom he asked if he could make a call to his family," Bruce said. "He got the telephone and put it on loudspeaker. He said 'I'm just about to sign'. I don't know how many brothers and sisters he's got but they all started singing. Then he started singing with them. It was quite bizarre.
"There must have been about 20 in the family and you could hear them all."
The Sunderland manager certainly has no qualms about Gyan's capacity to adjust to the rigours of English football.
"Physically, Africans are better than most," he said. "They can handle the demands. They are fairly brutal. You watch these African Nations Cup games and they tear into each other. I don't think adapting is going to be a problem for Asamoah."