From another web site:
The earliest known pipe organ, the hydraulis, invented in the
third century BC, ingeniously used water to maintain the pressure in its
wind chest. This animation illustrates the mechanism:
This reproduction instrument at Bath illustrates some of its potential for sound:
No wonder the Byzantine emperors used it in their court ceremonies. This German reconstruction sounds much more refined:
No wonder Mozart referred to the pipe organ as the King of Instruments and it has been acclaimed as the most complex engineering of man up to the modern era!