Complex sentence: The bells of St Mary's were heard leading the ringing that marked the centenary of Australian Federation, and are rung as part of the finale to Sydney's Symphony in the Domain concert in January, in unison with Tchaikovsky's 1812 Overture.
Split into simpler sentences: The bells of St Mary's were heard leading the ringing which marked the centenary of Australian Federation. They are also rung as part of the finale to Sydney's Symphony in the Domain concert in January, in unison with Tchaikovsky's 1812 Overture.