How it began
The hydraulis was invented in the 3rd century BCE by Ctesibius of Alexandria, a Greek inventor and mathematician working in Ptolemaic Egypt. Tradition says he began as a barber, and he may have been the first head of the Museum of Alexandria. Britannica describes the instrument as the culmination of earlier attempts to give a mechanical wind supply to a large set of panpipes. The Roman architect Vitruvius later described the water organ in De architectura and credited the force pump to Ctesibius.
How it works
The pipes stood on a wind chest connected to a cone-shaped wind reservoir, which one or two pumps supplied with air. The open bottom of the cone sat in a tall container half filled with water. When air pressure in the cone dropped, water rose inside it and compressed the air again, so the pipes sounded evenly. The player operated keys, or on some instruments sliders, that let air into the pipes. The keys were balanced and could be played with a light touch. It needed a human player and was not an automaton.
How it spread
The hydraulis was used at outdoor public entertainments, where its loud and penetrating sound carried. It spread through the Greek and Roman world: an instrument of the 1st century BCE was excavated at Dion in Greece and is kept in the museum there, and the Latin poet Claudian described its playing in the late 4th century CE.
Who pushed back
Use of the hydraulis declined in the West by the 5th century CE, though Arab writers of the 9th century still referred to it. Knowledge of how it worked faded over the following centuries, and later medieval writers wrongly thought it had been a steam-whistle organ like the calliope.
What lasted
The hydraulis is described as the first keyboard instrument and the predecessor of the church pipe organ. Ctesibius's related work on pumps also lasted: force pumps of the kind he described have been found at Roman sites, including Silchester in Britain.
