In ancient Greece they were essential: they whispered secrets to audiences, lent advice to heroes and passed judgment on royalty.
Fast forward a few thousand years and Canberra has one of its own - a chorus of citizens that gathers in public to sing laments over war and warnings about climate change.
To help celebrate the centenary of Canberra the group, ''A Chorus of Women'', will sing about the spirit of the capital in a free public performance in the National Library foyer.
The group gained widespread media attention when it formed nearly 10 years ago to sing a lament inside Parliament House on the day the former prime minister John Howard announced Australia's entry to the Iraq war.
Glenda Cloughley, of Griffith, said the plan spread via email and phone and 150 singers successfully entered Parliament House to give vent to their feelings, while many more protesters stood outside.
''We figured we had started something and we received invitations to sing in other places,'' she said.
''We are not just a choir - we are trying to voice what's happening in the public arena.
''We have continued singing and have done about 150 public performances.''
Johanna McBride, of Farrer, said the chorus sang original music written by its members.
''The group is totally open and the numbers change, people come in and out as to their capacity and their engagement with whatever issue we are involved with,'' she said.
''On Friday there will be four of us. It is an ensemble of very experienced singers.''
The chorus is performing as part of a program of free events titled The Musical Offering, which began on Tuesday evening to celebrate Canberra's centenary year.
Helen Moore, who is one of the organisers of The Musical Offering series, said the program was a gift to Canberra.
''We think it is a wonderful way for musicians to build their profile and the profile of Canberra as a city of music,'' she said.
A Chorus of Women will sing for about 25 minutes on Friday, with one of its songs giving a voice to Ethos herself: the angel-like statue outside the ACT Assembly.
She is meant to represent the spirit of the capital.
''It is an anthem for the Canberra community,'' Ms Cloughley said.
The statue's sculptor, the late Tom Bass, provided the words for the anthem and Ms Cloughley set it to music.
The chorus sings an a capella version of the song, but there is also a jazz version and Ms Cloughley said she would be happy to have the work reinterpreted by others.
''We hope it will inspire people with other musical tastes to make their versions of the song, maybe a rock version or a rap version,'' she said.
''We would encourage people to make their own versions and share them with us.''
The chorus will perform on Friday, January 4, at noon in the National Library.
For more details about the group visit: www.chorusofwomen.org