(from Gk. hudōr: ‘water’ and aulos: ‘pipe’ or aulē: ‘chamber’).
The ancient water organ (an Aerophone), an important musical instrument of later classical antiquity and the direct ancestor of the modern pipe organ. It is to be distinguished from the hydraulic or Water organ. In the latter the wind supply comes from air compressed by continuously flowing water. The hydraulis is bellows blown (by hand or by windmill), but water is used to stabilize the wind pressure.
JAMES W. McKINNON
Ancient Greek writers on music, for example, Athenaeus, Pseudo-Plutarch and Pseudo-Aristotle, very often named the inventors of musical instruments; these inventors, however, are generally mythical figures or men who long postdate the instrument’s first appearance. The inventor of the hydraulis is a significant exception, for all the evidence suggests that it was an Alexandrian engineer named Ctesibius, who lived in the 3rd century bce and was less remarkable for his theoretical ability than for his highly ingenious solutions to practical problems. He was the first to use air pressure to operate mechanical devices, in particular the pump with plunger and valve, the water clock, the pneumatic catapult and the hydraulis. He described his work in the Commentaries, a book frequently cited in classical times (for example by Vitruvius and Pliny the Elder) but no longer extant.
The invention of the hydraulis was first attributed to Ctesibius by Philo of Byzantium, an engineer of the late 3rd century bce, who if not actually Ctesibius’s pupil was much under his influence; he described the hydraulis as a ‘syrinx played by the hands’. Vitruvius, the famous technical writer of the 1st century ce, also attributed the hydraulis to Ctesibius and gave one of the two extant descriptions of the instrument. The other description is by Hero of Alexandria, a mathematician and engineer of the late 1st century ce; although he did not mention Ctesibius explicitly, both ancient and modern authors generally believe that Hero’s description of pneumatic devices was dependent upon Ctesibius.
Taking into account these facts and the absence of any references to the hydraulis predating Ctesibius, there is strong evidence for attributing its invention to him. Moreover, it is particularly plausible that the hydraulis should have been the invention of a single individual and should have originated in Alexandria at the time in question. The invention was not, as Sachs suggested, simply a matter of joining a panpipe to a new wind mechanism, since it also involved a highly sophisticated wind chest and keyboard. The hydraulis, then, did not have the elemental evolutionary origin of most ancient musical instruments. It was a complex machine involving more new elements than old, and therefore precisely the kind of invention that might be expected from the 3rd-century Alexandria of Euclid, Eratosthenes, Archimedes and Ctesibius. Accordingly it was first looked upon as a mechanical marvel as much as a musical instrument.
Approximately 40 representations of the hydraulis survive in mosaics, vases, coins and sculptures. Judging from these, the overall height of the typical instrument was about 165–85 cm, the base, often octagonal in shape, being about 30 cm high and 90 cm in diameter. On top of the base was a brass cistern seemingly covered with decorated wood; it might be cylindrical, octagonal or rectangular, 60–90 cm in height, of a diameter somewhat less than that of the pedestal, and was usually flanked by a pair of cylindrical pumps. Resting on the cistern was a rectangular wind chest, of about the same size as the base, topped by the pipes whose overall height represented from a third to half the total height of the instrument. The number of pipes appearing in a rank ranged from four or five to 18, eight being roughly the average. There were no more than four ranks. Normally only the front of the instrument was shown, with the organist looking out over the pipes. On the exceptional three-dimensional views, such as that on the Carthaginian lamp (see fig.1), the player is seen seated at a keyboard which extends from the wind chest.
There are two complementary descriptions of the mechanical aspects of the organ, that of Vitruvius (De architectura, x.8.3–6) and that of Hero of Alexandria (On Pneumatics, i.42). Vitruvius, writing in the 1st century bce, included developments such as the use of two pumps rather than one and of a wind chest that allowed ranks of pipes to be played separately. Hero, though writing in the 1st century ce, described the original, somewhat simpler instrument of Ctesibius. The description below is a composite of the two; it deals first with the wind-producing mechanism and then with the keyboard and wind chest.
It is from the wind-producing mechanism that the instrument derives its name, since Ctesibius used the tendency of water to seek its own level to supply a steady flow of air as opposed to the ebb and flow produced by bellows. Fig.2 shows a pump-handle A operating the plunger B within the cylinder C and forcing air into the conduit D. The valve E allows air to enter the cylinder when the plunger is depressed and prevents it from escaping when the plunger is raised; the valve F prevents air from returning to the cylinder when the plunger is depressed. The air then entering the pnigeus G forces the water level in the cistern H upwards, since the water has access to the pnigeus by apertures I at its base. While the plunger is being depressed in preparation for the next stroke the weight of the receding water maintains air pressure in the pnigeus and consequently a steady flow through the conduit J to the wind chest.
Fig.3 shows how the air, once it has reached the wind chest, is distributed to the pipes. The finger depresses key A which, pivoting on point B, pushes slider C along a track in the chest until hole D is in alignment with the bottom of the pipe and hole E, thus allowing the compressed air within the wind chest to enter the pipe. When the player lifts his finger from the key, spring F returns the slider to its original position.
Vitruvius described a chest with four, six or eight channels, each running beneath a separate rank of pipes and opened or closed by a valve fitted with an iron handle. This stop action is very simple in conception, being nothing more than a division of the wind chest into separate compartments. However, it creates serious practical difficulties, particularly for the slider, which is subject to an increase in both friction and the leakage of air. Modern experiments, particularly those of Jean Perrot, indicate that the difficulties become insuperable with more than four ranks, a conclusion confirmed by ancient iconographic and archaeological evidence. Vitruvius, using the terms tetrachordal, hexachordal and octochordal, was evidently indulging in a kind of theoretical symmetry.
Vitruvius and Hero were technical writers who limited their descriptions to the instrument’s mechanical functioning; it is possible to speculate only on the most basic musical aspects, of which timbre and pitch are the most significant.
The central question concerning timbre is whether the hydraulis had not only flue pipes but also reeds (as several organologists have maintained). On the positive side is the name of the instrument, with its ostensible reference to the aulos, a reed pipe instrument. On the other hand, the name may refer to aulē, a chamber, and thus be a reference to the instrument’s distinctive ‘water chamber’. There are also literary references to the instrument’s widely differing tone quality, at one time sweet, at another powerful. Organologists have tended to associate the latter quality with reed pipes. Yet, surviving representations do not at all suggest reed pipes. The absence of anything resembling the bulbous holmos of the aulos is particularly noteworthy. Also very much to the point is Walcker-Mayer’s reconstruction of the Aquincum organ’s pipes with the same kinds of metal as were used in the original pipes. The organ has four ranks, all of flue pipes, three being stopped and one open. He found both open and stopped to be entirely unlike any modern pipes in timbre, the open being particularly harsh and shrill and the stopped being only somewhat less harsh with a kind of throaty rattle. The case for reed pipes, therefore, has yet to be proven, and it is seriously anachronistic to assume that the variety of tone suggested by the literary sources takes the form of a contrast between, for example, a soft flute stop and a loud reed stop in a modern organ.
The question of pitch and its corollary tonality is even more difficult to resolve. Archaeological remains might be expected to provide a firm basis for a hypothesis, but Walcker-Mayer and Perrot, who studied the pipes of the Aquincum organ, came to radically different conclusions, the former maintaining that the instrument was diatonic, the latter that it was chromatic. Study of the pictorial evidence is similarly inconclusive. The method normally employed consists of measuring the longest and shortest pipes to determine the instrument’s range, counting the number of pipes and then filling in the intermediate pitches and establishing the tonality. Underlying this method, however, is the fallacious assumption that each representation was a precisely scaled depiction of a particular instrument rather than a conventional schematization. Perhaps the most serious specific problem concerns the angle of the slanting line, which is nearly always straight, described by the tops of the pipes. If the artists had been attempting realistic depictions, the line, while not necessarily reproducing the logarithmic curve created by a chromatic rank of equal-tempered pipes, would certainly have described something other than a straight line. Moreover, only a minor variation in the length or number of pipes is required to change the presumed tonality from one genus to another. This is particularly true if the organologist presumes to decide whether conjunct or disjunct tetrachords are involved.
Theoretical sources provide what is possibly the least valuable evidence for determining pitch, since a wide gap separates the theory of late antiquity (with its mathematical bias) from musical practice. But even ignoring this gap and taking the sources literally, as several historians of the organ have done, leads to unsatisfactory conclusions. The conventional starting point is Bellermann’s Anonymous (28; ed. Najock), which asserts that the hydraulis players use only the Hyperlydian, Hyperiastian, Lydian, Phrygian, Hypolydian and Hypophrygian tropoi. But the accommodation of even these six tropoi would seem to have required more pipes than that provided by the typical Roman hydraulis. In attempting to cope with this problem organologists have tended to opt for one of two alternatives, both of them unsatisfactory. According to the first, each organ was tuned in one tropos only; there were thus Hyperlydian organs, Hyperiastian organs etc. According to the other, each rank represented a different tropos; in this case an instrument would have been confined to four of the six desired tropoi and in fact less than their entire ambitus. Moreover, there would have been an uneconomical duplication of pitch and the preclusion of using more than one rank at a time.
In summary, it seems that the state of the evidence allows for only the most general of conclusions. Pictorial evidence indicates a relatively high tessitura for the pipes and a relatively small compass for each rank; and literary sources suggest a certain amount of versatility in dynamics if not in timbre. Except for the remarkably precise knowledge gained from Vitruvius and Hero of the instruments’s mechanical functioning, the degree of uncertainity surrounding the hydraulis is similar to that concerning other ancient instruments. Whether the hydraulis was used to play polyphonic music is, again, uncertain; it appears to have had the capacity to play at least in two parts. All literary, pictorial and archaeological evidence indicates that the keys were depressed by the fingers, and with relative facility. Yet to what extent such possibilities were exploited or in what musical direction they tended (for example, drones, parallelisms) is not known.
Although the hydraulis was at first viewed as a marvel of mechanical ingenuity, its musical potential was realized in a relatively short time. The claim of Athenaeus that Ctesibius’s wife Thais was the first organist has an apocryphal air about it, but there is no reason to doubt a Delphic inscription decribing the success of the hydraulis player Antipatros in the agones of 90 bce.
Texts mentioning the hydraulis, particularly at Rome, multiplied during the following centuries. Suetonius wrote of Nero’s infatuation with the instrument; the Aetna poem placed it in the theatre, and Petronius referred to its being played at chariot fights in the arena.
There are approximately 50 known literary references to the instrument and rather fewer pictorial representations. The impression they create is of an instrument in rather general usage, if not so common as the smaller and presumably less expensive kithara and tibia. It was found in the homes of the wealthy, the theatre and the arena, this last setting being the most characteristic, particularly in pictures, where it is shown sometimes alone but more often playing with brass instruments like the Cornu and tuba (see Tuba (ii); see also Organ, §IV, 1, fig.22).
Another type of hydraulis, replacing Ctesibius’s hydraulic pump with bellows, was at first less prominent than the hydraulis proper. Bellows had been in use long before the invention of the hydraulis but were not practical for musical purposes because they could supply only intermittent air pressure. However, it seems to have been simple to adapt Ctesibius’s principles by replacing the cistern with a flexible leather reservoir, weighted on top, fitted with valves to prevent the escape of air and fed by one or more bellows. This device had the advantages of being lighter in weight, cheaper, and less liable to corrosion.
The earliest extant reference to the pneumatic instrument is from Pollux, the rhetorician of the 2nd century ce, who described it as smaller and less powerful than the hydraulis. The Aquincum organ, with its dedicatory plate from 228 ce, was probably of this type, since there is no trace of a bronze cistern and pnigeus associated with the substantially preserved pipes and wind chest (see Organ, §IV, 1, fig.23). Julian the Apostate (332–63) seemed to be describing the pneumatic organ when he mentioned a bag of bull-hide feeding the pipes, as is the case with the 5th-century bishop Theodoret of Cyrrhus, who compared the bellows of the organ to the human lungs.
These texts suggest that the more practical pneumatic organ came to replace the hydraulis in the Eastern Empire during late classical times. Meanwhile the hydraulis disappeared in the West with the collapse of the Western Empire in the 5th and 6th centuries. The pneumatic organ maintained a place of some prominence in the court at Byzantium and found its way into the West when Emperor Constantine Compronymus in 757 presented a small organ to Pepin the Short, King of the Franks.
From that time there began the dramatic development of the Western pipe organ. Pictorial and documentary evidence overwhelmingly demonstrates that it was a pneumatic organ; the hydraulis was mentioned only in confused invocations of the classical past. For example, the 11th-century Berne Anonymous, after a careful description of the bellows organ, states that the pipes can be made hydraulic by simply placing beneath them a cistern of water, which the air sucks through the pipes causing them to sound. Even after Vitruvius’s De architectura was popularized in the Renaissance, an expert such as Bédos de Celles, confusing the hydraulis with the water organ, was able to believe that the hydraulis was powered by a waterfall, and he marvelled at the alleged construction by the 10th-century monk Gerbert of a hydraulis in a church in an area where rivers and streams are rare.
The first author to give an accurate description of the instrument may have been the architect Claude Perrault in his Abregé des dix livres d’architecture de Vitruve (1673, 2/1684). The general confusion, however, was not dispelled until early in the 20th century by projects such as Galpin’s reconstruction (c1900) and Degering’s excellent monograph. Jean Perrot and Werner Walcker-Mayer have produced modern reconstructions of considerable accuracy.
For further discussion of the hydraulis see Organ, §IV, 1.
H. Degering: Die Orgel: ihre Erfindung und ihre Geschichte bis zur Karolingerzeit (Münster, 1905)
H.G. Farmer: The Organs of the Ancients from Eastern Sources (London, 1931)
F.W. Galpin: A Textbook of European Musical Instruments (London, 1937, 3/1956/R)
W. Apel: ‘The Early History of the Organ’, Speculum, xxiii (1948), 191–216
J. Perrot: L’orgue de ses origines hellénistiques (Paris, 1965; Eng. trans., 1971)
W. Walcker-Mayer: Die römische Orgel von Aquincum (Stuttgart, 1970; Eng. trans., 1972)
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E.L. Szonntagh: ‘Is the Pipe Organ Discovered at Aquincum a Water Organ?’, Scientific Honeyweller, ii/4 (1981), 54–60
P. Williams: The King of Instruments: How Churches Came to Have Organs (London, 1993), 1–39
P. Williams: The Organ in Western Culture, 750–1250 (Cambridge, 1993), 235–52
T.J. Mathiesen: Apollo’s Lyre: Greek Music and Music Theory in Antiquity and the Middle Ages (Lincoln, NE, 1999), 225–30