At Easter (and during other holidays) Lau and a group of musicians with the Hong Kong Pops Wind Orchestra performed lunchtime concerts for sick children in cancer and other wards in the Kowloon hospital.
He has been at the hospital since 1996 after graduating and working in England. He was a doctor in the children's cancer ward before moving to work in the accidents and trauma department, but he has not forgotten his previous posting.
"It's a sad ward," Lau, 42, says. "The children are isolated and can stay in the hospital up to six months while undergoing many treatments. Their lives are hard and they can be a bit bored. Apart from watching television and doing activities with nurses, they have nothing else to do. I want to give them something more - something to cheer them up."
Lau has loved music since he was a teenager and began to play the saxophone in Form Four. He teamed up to play with a group of professional musicians - the Hong Kong Pops Wind Orchestra, a non-profit organisation - after watching them perform at the hospital. The musicians, all graduates from the Hong Kong Academy for Performing Arts (APA), offer their services for free.
Maria Wong Ka-yee, the orchestra's co-ordinator and a clarinet teacher at the APA, says the parents of some of her pupils work at hospitals, which gave her the idea of staging free concerts for patients and staff.
"I've always been interested in community service and thought we can bring joy and entertainment to people through our music," she says.
The musicians have been performing at the hospital since December 2008. "The hospital has been very supportive," Wong says. "We hope our music can warm the patients' hearts and, at the same time, soothe and lighten the heavy workload of staff."
Lau often performs three operations a day and sees patients at the hospital's clinic twice a week. But he still finds time to play music for patients whenever he can.
"I help my patients to regain their physical health through being a doctor. And I play music to comfort and heal their emotional needs. To me, it's the same thing," he says.
"Being sick and in hospital can make a person feel grey. So I hope our music will bring some happiness to patients."