Mr Morrison and his wife took over the organisation of the annual event about 20 years ago. They put posters inside the hospital about two weeks before Christmas and sang with whoever turned up on the night.
Mr Morrison said about 70 people took part this year, including hospital staff and relatives of patients.
Some carollers returned each Christmas Eve to spread the festive spirit, he said.
''It brings a lot of warmth to people stuck in hospital over Christmas time,'' he said.
The carollers began at the children's ward at 6.30pm and made their way around all wards as well as the intensive care unit.
''Sometimes ICU patients are unable to have us go in there, but this year the staff asked us to go in and it was lovely.
''There were a few tears shed,'' Mr Morrison said.
It took about two and a-half hours to get around all the patients, and carollers were delighted to see some children dancing in the hospital halls, he said.
REPORT: ROSIE MANINS / PHOTO: PETER MCINTOSH