hydraulus

This organ, called hydraulus, or organum hydraulicum, from the water used in the blowing apparatus, enjoyed great popularity.

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

It would be strange, however, if this important means of regulating the wind pressure had been discontinued while the hydraulus was still in vogue.

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

Thus the double control of the pipes by means of channel and slide was again used as in the hydraulus, but with exchanged functions, the channel now serving for the key action and the slider for the stop action.

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

About the fourteenth century, it appears, the slider for the key action had been discontinued, and channels (grooves) had been used, as in the ancient hydraulus, but running transversely, each under a row of pipes belonging to the same key.

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

In the early centuries the objection of the Church to instrumental music applied also to the organ, which is not surprising, if we remember the association of the hydraulus with theatre and circus.

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

Thus, after an interval of about a thousand years, the blowing apparatus regained the perfection it had possessed in the hydraulus during the preceding thousand years.

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

Ctesibius, the inventor of the hydraulus, and the Venetian Georgius, who built the first organ north of the Alps, have already been mentioned, It is interesting to find a pope among the organ-builders of history: Sylvester II (999-1003), who seems to have built a hydraulic organ (Pretorius, "Syntagma Musicum", II, 92).

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

Another point in which the medieval organ was inferior to the hydraulus, was the absence of stops.

The Catholic Encyclopedia, Volume 11: New Mexico-Philip 1840-1916 1913

(mosaics), where the buccinator is accompanied on the hydraulus.

Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" Various