Monday, 8 August 2016

Hydraulis: The water-powered keyboard

The water organ, also known as a hydraulis, is thought to be the world’s first keyboard instrument, and oldest pipe organ. The name ‘Hydraulis’ comes from the Greek for water, ‘hydra’, and pipe, ‘aulos’.

An engineer from the 3rd century BC, Ctesibius of Alexandria, is credited with its invention. It is highly unusual for us to know the name and identity of the inventor of such an ancient object, since for many instruments all that it known is that they were believed to have divine or mythical creators.

The ancient hydraulis was played by hand, and the sound was controlled by the player pressing lightly on balanced keys or sliders. This is in contrast to the Renaissance pipe organ, which played automatically with the flow of water.

The organ is driven by water, which enters a wind chamber (camera aeolis) from above through a pipe. Air is introduced via a side pipe, compressed and driven upwards into a wind trunk or chest. This is used to blow the pipes, while two diaphragms or ‘splash-plates’ shield the pipes from water spray.

In some designs, the water comes out of the wind chamber and powers a water wheel, which drives a cylinder. A tap above the instrument must be opened for the instrument to run, and it will continue to play until the tap is closed.

These diagrams show the workings of the hydraulis (via
The player would pump from point A, on the left diagram, forcing air through pipe D. Valves ensure the air does not flow backwards. The water pressure pushes air up through pipe J, and into the wind chest.

On the right, we see a close-up of a pipe. The player plays the key at A, which moves the glider C, allowing pressurised air to escape through the pipe when D and E align. F is a quill that dictates the end of the note by closing the gap.

The mechanics of water organs are discussed in various ancient sources: in writings by Ctesibius himself and Philo of Byzantium from the 3rd century BC; accounts by Vitruvius, a Roman engineer, architect and author of De Architectura, from around 20 AD; and those by Hero of Alexandria, from around the year 62 AD. 

Depictions of the instrument have been found in mosaics, paintings, as well as on coins, and even oil lamps. These have helped historians piece together what the hydraulis looked like, and when and where it might have been played.

These oil lamps were made in the shape of water organs, and can be found in museums at Copenhagen and Carthage today. (via

A coin featuring a water organ, dating from the time of Nero. (via

It appears the water organ was widely used for outdoor entertainment, at public events and festivals, probably because of the loud, deep sound it produces.

The mechanisms of the water organ were discovered with the help of partial remains, such as those found in Budapest in 1931, which were inscribed with the date 228 AD. Although most of the instrument had decomposed over time, the metal mechanism was still intact. From this, a working replica was built, which can be seen in the Aquincum Museum in Budapest today. The museum is named after the ancient ancestor of Budapest, a Roman city called Aquincum.

The reconstructed hydraulis in action (via
Another important relic was uncovered in 1992 by archaeologists in the Greek city of Dion, which was an ancient Macedonian city near Mount Olympus. They believe they have recovered fragments of a hydraulis from the 1st century BC. A working replica was completed by the European Cultural Centre of Delphi in 1999, which is on display in the Museum of Dion, along with the fragments.

The fragments of a first century BC water organ at the Museum of Dion. (via 
Very little is known about what kind of music was played on these ancient instruments, but it is amazing that the low, penetrating sound of the pipes can be recreated for us to hear thousands of years after its invention.

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