The Grey Shrike Thrush is a quite a common bird and particularly well known for it’s magnificent song. Often referred to a GST by birders or twitchers, you will hear them throughout the bush and suburban neighbourhoods.
For such a common bird, the description in Wikipedia is very short. Perhaps a search on eBird or other bird sites will provide more information.
Wikipedia Description
Of medium size (about 24 cm or 9.4 in long) and lacking bright colours, the grey shrikethrush—usually just thrush in casual conversation—has an extraordinary gift for ringing melody, unmatched by any other Australasian species save perhaps the two lyrebirds and its northern relative, the sandstone shrikethrush.