Sydney Opera House workers treated to construction site performance from Sydney Symphony Musicians play to Opera House workers yesterday. THEY are used to performing inside the Opera House - now the Sydney Symphony has played underneath it. Workers tunnelling under the landmark building were treated to a live performance by a brass ensemble on Wednesday. Sydney Symphony managing director Rory Jeffes said the performance was to thank the workers for improving the world-famous site: "It's an initiative that came from the musicians. For the past year they've been walking past all the construction work and they know it is going to transform the experience and they wanted a chance to say thank you. There was an amazing acoustic down there. I think we're going to have to turn this into another performance space. The music was the same piece played to workers and their families when the Opera House opened in 1972. The $152 million Vehicle Access and Pedestrian Safety project has been under way since 2011, an is expected to be completed by mid-next year. For them, it was about continuing that same tradition from 40 years ago in a slightly smaller way. The $152 million Vehicle Access and Pedestrian Safety project has been under way since 2011, with work expected to be completed by mid-next year. Opera House chief executive Louise Herron said it was the biggest project since the structure was built. "We are building a tunnel so heavy vehicles can come straight in off Macquarie St and come underneath into the belly of the Joan Sutherland Theatre and also the concert hall," she said. It means all the areas where the trucks would have gone across the forecourt are returned to the public, making it a lot safer for the workers and more efficient.