The contract, entered into by music trio the Bee Gees - Barry, Robin and Maurice Gibb - in March 1959, was located during an audit of the firm's safe custody documents.

Practice development manager Jacki Wilson explained that Carter Newell got possession of the document some years ago when it merged with former Brisbane firm Feather, Walker & Delaney.

The Bee Gees began their musical careers while living in Brisbane and Feather, Walker & Delaney represented their original promoters - Bill Goode, William Gates and John Proctor.

Once she got over her initial excitement of uncovering the document, Wilson began the process of tracking down the promoters.

"We jumped on the electoral roll, we Googled, we searched around until we eventually tracked them down and were able to write to them," she said. After lengthy deliberations, the firm and promoters reached an agreement to return the contract to the Gibbs family, which was reached on March 19 of this year - 50 years to the day since the original contract was signed.

"We wanted the document out of our safe custody and we thought that this was an important document so it should be either offered to the Gibbs family or to the state archives or someone like that because it's a piece of history," Wilson said.

Tracking down the oldest Gibb brother, Barry, posed another challenge for Wilson, but she says she was surprised at how easy it turned out to be. "I thought it was going to be quite difficult ... but people in the industry - through word of mouth and the odd email here and there - were able to get back to him relatively quickly. I think they recognised that it was probably a document that needed to be returned to him - it wasn't just a run-of-the mill thing," she said.

The contract is now safely back with Barry in the US, and according to Wilson, the family is considering putting it on display at the Rock and Roll hall of Fame in Cleveland, Ohio.

"It's nice to [have given] the document back," she said. "It was a unique [experience] - not something you do every day in legal practice. It's just our little touch with the rock and roll world."