Forgotten Songs (Angel Place)

Look up. One hundred and eighty empty bird cages are suspended above this narrow laneway, and if you stop and listen, you will hear birdsong coming from them. Not real birds -- recordings of fifty species that once lived in central Sydney before urbanisation drove them out. You are surrounded by ghost music from birds that no longer exist in this part of the city.

The installation is called Forgotten Songs, and it does something clever with time. During daylight hours, you hear daytime species. As the sun sets, the soundtrack shifts to nocturnal birds -- owlet-nightjars, powerful owls, tawny frogmouths -- and the triggers adjust automatically for longer summer days and shorter winter ones. Come here at noon and you hear one city. Come at midnight and you hear a completely different one.

Look down at the ground beneath your feet. The names of all fifty bird species are embedded into the pavement. You are literally walking over their names while their songs play above your head. It is a memorial without a plaque, a funeral without a body.

The artist Michael Thomas Hill created it as a temporary installation in two thousand and nine. It was supposed to come down after a few months. But people loved it so much that the city made it permanent in two thousand and eleven as part of a nine-million-dollar laneway art program. A temporary artwork about things that disappeared became the one thing that stayed.

This is one of those spots that rewards you for being curious. Most people walk down Angel Place -- it connects George Street to Pitt Street -- and never look up. The cages are small and the laneway is narrow and shadowed. You have to stop, tilt your head back, and actually listen. Then it hits you.