 City Recital Hall is dedicated mainly to chamber music and chamber orchestra concerts, featuring many famous international artists as well as concert series by local groups such as the Australian Chamber Orchestra and Sydney's foremost Baroque orchestra, the Australian Brandenburg Orchestra.Opera Australia, as at 2015 the world's third-busiest opera company, has its headquarters in Sydney and performs a busy program of mainly classical and occasionally contemporary operas at the Opera Theatre of the Sydney Opera House.New experimental and avant-garde music is performed by Ensemble Offspring, Halcyon, The Noise and others, at the recently refurbished Carriageworks and many small inner-city cafes, warehouses, theatres etc.