An Edwards bass trombone stolen from the Sydney Opera House will soon be reunited with its owner.

The trombone, which was stolen on January 1, was anonymously handed in to police on Wednesday.

The instrument, which costs about $8900 and belonged to freelance musician Colin Burrows, was taken from a locker room at the Opera House on New Year's Day.

"The case is still under investigation but what we can say is that the trombone was handed to us on March 4," Sydney City police station duty officer, Peter Vromans, said.

Police said the trombone was stolen between 2.40am and 2.50am on January 1 and have released several photos of a man who might be able to "assist with inquiries".