The water organ or hydraulic organ is a kind of pipe organ .
The water organ or hydraulic organ ( early types are sometimes called hydraulis , hydraulos , hydraulus or hydraula ) is a type of pipe organ blown by air , where the power source pushing the air is derived by water from a natural source ( e.g. by a waterfall ) or by a manual pump . Consequently , the water organ lacks a bellows , blower , or compressor .