The beginnings of the organ can be traced back to the collection of fixed-pitched pipes blown by a single player such as the panpipes. The first examples of pipe organs with the basic features of today can be traced to the third century BCE. It is said to have been invented by Ktesibios of Alexander and contained “a mechanism to supply air under pressure, a wind-chest to store and distribute it, keys and valves to admit wind to the pipes, and one or more graded sets of fixed-pitch pipes.”
Early organs used water as a means to supply air-pressure. Up until the eleventh century, the pitch and range of organs were extremely limited, mainly in part to the lack of a keyboard. Keys of a sort were introduced around this time, though not in the manner we are accustomed to. The earliest keyboards were sets of levers played by the hands rather than the fingers. Circa 1400, the keys became smaller and more numerous until they began to resemble the modern keyboard. The uniformity of the Catholic church helped perpetuate the use of organs throughout Europe
“The pipe organ is to be held in high esteem, for it is the traditional musical instrument that adds a wonderful splendor to the church’s ceremonies and powerfully lifts up the spirit to God and to higher things” (Constitution on the Sacred Liturgy # 120).