Police have appealed for help in solving the mystery surrounding the bashing death of long-time AC/DC manager Crispin Dye in Sydney more than 20 years.

Singer-songwriter and band manager Crispin Dye had been celebrating the release of his debut record with drinks in Sydney when he was bashed to death a day before Christmas Eve in 1993.

Numerous investigations, including a coronial inquest in 1995, have failed to shine much light on the case.

Now police are offering a $100,000 reward for information leading them to the killer of the long-time AC/DC manager in an inner-city street.

The 41-year-old Queensland man had been in Sydney visiting family, and had gone out drinking in Surry Hills to celebrate the release of the record when he was attacked and robbed of his wallet.

He died from his head injuries in hospital on Christmas Day.

Despite the assault having occurred during a spate of gay-hate murders in the `90s, detectives do not think the attack was motivated by homophobia.

Mr Dye’s 91-year-old mother, Jean, says her son was a gentle man.

“He was very, very popular and I don’t think he had any enemies, I really don’t,” she told Macquarie Radio on Wednesday.

“When he passed away, on Christmas Day, is was just beyond all comprehension.”

A witness at the time reported seeing three young males possibly of Pacific Islander appearance, aged in their late teens or early 20s and dressed in baggy pants and shirts standing over Mr Dye’s unconscious body.

Police are hoping the reward will prompt people to come forward with information and help to finally bring some closure to Dye’s loved ones.

“We know that there are people out there who know who is responsible for Crispin’s death,” Homicide Squad Commander Mick Willing said.