Land subsidence is perhaps the very slowest of man-made disasters. It moves almost in geological time, without the sudden drama of an earthquake or tsunami. Quietly, mournfully, Jakarta is sinking into the sea, a constant movement too slow for human senses to register. Its pace is out of sync with Jakarta’s attention span, jostled here and there by urgent daily problems. It is thus easily forgotten, until it makes itself known with every king tide, or river flowing surreally backwards.

The cause is easily identified. Factories, malls and apartment blocks ensure they get a steady supply of water by boring into the third aquifer below Jakarta, at a depth of 300 metres. The water is used to flush away chemical residues in factories, or it fills rooftop swimming pools with views to the sea. The pace of extraction is out of sync with the replacement rate of underground hydrological cycles, but in line with the city’s thirst for development.

This piece of music uses data on the rate of land subsidence in several sites along Jakarta’s coast since 1979, condensing and mapping a 40 year downward trajectory into a 4 minute song, a favoured block of time for listening and committing to memory. The song is composed from samples of Ismael Marzuki’s classic keroncong ballad, ‘Bandar Jakarta’, a nostalgic ode to Jakarta Bay. As the piece progresses it is slowly sunk, gradually losing its higher frequencies and deteriorating into a deep distorted, mournful refrain.

The four speakers spread across the room play the sinking of specific sites on Jakarta’s north coast – Kamal Muara, Pantai Mutiara, Ancol and Cilincing. They play the same song but distort at different paces, reflecting the highly localised way land subsidence occurs. The space where this work is exhibited, the now permanently flooded women’s prison of the former Batavia town hall, plays its part as the basement waters assist in dampening the song’s higher frequencies.