The Australian Haydn Ensemble, a period instrument group specializing in chamber music and string orchestral music of the classical era, will perform Sunday, Jan. 19, 4-5 p.m., at Wilton Library, 137 Old Ridgefield Road. They will present a program of classical string pieces on original instruments in the style intended by the composers. Each member of the ensemble is a specialist in historical performance. Their collaboration results in a powerful strength of tone. This concert is free and registration strongly suggested. Information: 203-762-3950, ext. 312 or wiltonlibrary.org.