in general, is an instrument or machine designed for the production of some certain action or operation; in which sense the mechanic powers, machines, and even the veins, arteries, nerves, muscles, and bones of the human body, may be called organs.
ORGAN, in music, the largest and most harmonious wind-instrument.
The invention of the organ is very ancient; though it is agreed that it was little used till the eighth century. It seems to have been borrowed from the Greeks. Vitruvius describes an hydraulic one in his tenth book of Architecture. The emperor Julian has an epigram in its praise. St Jerom mentions one with twelve pair of bellows, which might be heard a thousand paces, or a mile; and another at Jerusalem, which might be heard at the mount of Olives.
The church-organ consists of two parts; the main body, called the great organ; and the positive or little organ, which forms a small case or buffet, commonly placed before the great organ. The size of an organ is generally expressed by the length of its largest pipe; thus they say, an organ of 8, 16, 32 feet, &c. The organ in the cathedral church at Ulm in Germany is 93 feet high, and 28 broad; its largest pipe is 13 inches diameter, and it has 16 pair of bellows.
The several parts of the church-organ are as follow. HHH is the sound-board: which is composed of two parts, the upper board or cover HHH, and the under board HI, which is much thicker than the other; each of these consists of several planks laid with their edges to each other, and joined very close together. In the under-side of the lower board there are made several channels, which run in the direction L.L, MM, &c. and are continued as far as there are stops in the organ, and come almost to the edge HK. These channels are covered over very close with parchment or leather all the way, except a hole that is commonly at the fore-end next HK, upon which a valve or puff is placed. These channels are called partitions. When this valve or flap is shut it keeps out the air, and admits it when open. On the upper side of the lower board there are likewise cut several broad square channels, lying cross the former, but not so deep as to reach them; these lie in the direction LN, PQ, &c. To fit these channels, there are the same number of wooden sliders or registers f, f, f, &c. running the whole length; and these may be drawn out or thrust in at pleasure. The number of these is the same as that of the stops in the organ.
KKK is the wind-chest, which is a square box fitted close to the under side of the lower board, and made air-tight, so that no air can get out but what goes through the valves along the partitions.
VV are the valves or puffs which open into the wind-chest; they are all inclosed in it, and may be placed in any part of it, as occasion shall require. One of these valves, with the spring that shuts it, and the wire that opens it, is represented by fig. 2.
C, D, E, F, &c. are the keys on which the fingers are placed when the organ is played: these keys lie over the horizontal bar of wood W, in which are stuck an equal number of wire-pins z, z, on which keys are fixed; and the keys move up and down on the bar, as on a centre. There is another bar, against which the keys fall when put down, and which is here marked: on this also are several wires, which go through the keys, to guide them; and on this bar a list is fastened to hinder the keys from knocking against the wood.
The keys are made to communicate with the valves several ways, as we shall now describe. First, s, s, s, are the key-rollers, moving on the pivots l, l; these rollers lie horizontally, one above another, and are of such a length as to reach from the valve to the key: a, a, a, are arms or levers fixed to the key-rollers: w, w, the valve-wires fixed to the arms a, a, and to valves V, and go through the holes b, b, in the bottom of the wind-chest: b, b, b, are likewise arms fixed to the key-rollers: d, d, d, the key-wires fixed to the arms b, b, and to the keys C, D, E. Now, when the end of any one of the keys C, D, E, is put down, it pulls down the arm b, by the wire d, which turns about the roller s with the arm a, that pulls down the wire w, which opens the valve that is shut by the spring as soon as the pressure is taken off the key. In this construction there must be a worm-spring fastened to the key, and to the bar W on the further side, to keep down the end s of the key.
Another method of opening the valves is thus: x, y, x, y, are slender levers, moveable on the centres 1, 1; 5 x, 5 x, are wires going from the further ends of the keys to the ends x of the levers; y V, y V, are other wires, reaching from the ends y of the levers, through the holes h, to the valves V. So that putting down the key C, D, &c. raises the end 5, which thrusts up the end x of the lever, by the wire 5 x; this depresses the end y of the lever, which pulls down the wire y V, and opens the valve V.
A third way of opening the valves is this: At the end of the key b, is a lever 8, 9, moving in the centre 7. This makes, with the key, a compound lever. From the end 9, a wire goes to the valve. Now the putting down the end 6 of the key, raises the end 8, which depresses the end 9, of the lever 8, 9, pulls down the wire, and opens the valve. There is only one of these drawn in the scheme, and but a few of the others, to avoid confusion.
R, R, are the rollers, to move the sliders, by help of the arms c, c, which are fixed horizontally in these rollers; k e, k e, are also levers fixed in the rollers; l e, l e, are the handles, which lie horizontally, and pass through the holes l, l; they are fastened to the lever k e, being moveable about a joint at e.
Now, any handle l p, being drawn out, pulls the end e toward l, which turns about R k, along with the arm c f; and the end f pulls out the slider f g; and when p is thrust in, the arm c f likewise thrusts in the slider f g.
Upon the several rows of holes which appear on the top of the upper board, there are set up an equal number of rows of pipes. The pipes of an organ are of two kinds; the one has a mouth like a flute, the other with reeds. The first, called pipes of mutation, consist, (1.) of a foot A A B B (fig. 3.) which is a hollow cone, that receives the wind that is to sound the pipe; (2.) To this foot is fastened the body of the the pipe BBDD. Between the foot and the body of the pipe is a diaphragm or partition FEF, that has a long but narrow aperture by which the wind comes out; over this aperture is the mouth BBC, whose upper lip C, being level, cuts the wind as it comes out.
The pipes are of pewter, of lead mixed with a twelfth part of tin, and of wood. Those of pewter are always open at their extremities: their diameter is very small, and their sound very clear and shrill. Those of lead mixed with tin are larger; the shortest are open, the longest quite stopped; those of a mean size are partly stopped, and have beside a little ear on each side the mouth, to be drawn closer or set further alunder, in order to raise or lower the sound. The wooden pipes are square, and their extremity is stopped with a valve or tampion of leather. The sound of the wooden and leaden pipes is very soft; the large ones stopped are commonly of wood, the small ones of lead. The longest pipes give the gravest sound, and the shortest the most acute: their lengths and widths are determined by a fixed proportion to their sounds; and their divisions are regulated by a rule, which is called the diapason. The longest has commonly 16 feet; but in very large organs it has 32 feet. The pedal tubes are always upon, though made of wood and of lead. Whatever note any open pipe sounds, when its mouth is stopped it will sound an octave lower; and a pipe of twice its capacity will likewise sound an octave lower.
A reed-pipe consists of a foot AABB, (fig. 4.) that carries the wind into the shallot or reed CD, which is a hollow demi-cylinder, fitted at its extremity D, into a fort of mould, by a wooden tampion G. The shallot is covered with a plate of copper KKLL, fitted at its extremity II, into the mould, by the same wooden tampion. Its other extremity KK, is at liberty: so that the air entering the shallot makes it tremble or shake against the reed; and the longer that part of the tongue IL, which is at liberty, is made, the deeper is the sound. The mould II, that serves to fix the shallot or reed, the tongue, tampion, &c. serves also to stop the foot of the pipe, and make the wind go out wholly at the reed. Lastly, in the mould is soldered the tube HH, whose inward opening is a continuation of that of the reed: the form of this tube is different in different ranks of pipes. The degree of acuteness or gravity in the sound of a reed pipe, depends on the length of the tongue, and that of the pipe CK, taken from the extremity of the shallot to the extremity of the tube. The quantity or intensity of the sound depends on the width of the reed, the tongue, and the tube; as also on the thickness of the tongue, the figure of the tube, and the quantity of wind. To diversify the sounds of the pipes, a valve is added to the port-vent, which makes the wind go out in fits or shakes. In fig. 1. X represents a flute-pipe of wood, Z a flute-pipe of metal, Y a trumpet-pipe of metal. The pipes, to prevent them from falling, pass through holes made in boards, placed upon the upper board.
The pipes are made to communicate with the wind-chest in the following manner. There are holes bored that go through the upper and lower boards, and through the slider, (when it is drawn out), into the partition below; so that any pipes placed upon those holes will then communicate with the partition, which, by its valve, communicates with the wind-chest. But when the slider is thrust in, its holes do not answer to those in the upper and lower boards; therefore the communication is stopped, so that no wind can get to the pipe.
To every large organ there must be at least two pair of bellows, which are marked in fig. 1. by TU, TU, O, O, are the handles, moving upon the axis n n, n n. Each of these bellows consists of two boards, the lowest of which is immovable; and in this there is a valve r, opening inwards, and a tube leading to it, called the conveying tube. There is also a hole in this under board, from which a tube leads to the port-vent, which is a square tube marked 4, rising upward, and inserted into the under side of the wind-chest at 2. In the tube leading to the port-vent there is a valve that opens towards the port-vent, and suffers the air to go up the port-vent, but not to return. Now the handle O being pulled down, raises the upper board T; and the air enters through the valve r; and when the handle is let go, the weight of the upper board, which carries three or four pound to every square foot, continually descending, drives the air through the port-vent to the sound-board: and as the bellows work alternately, one pair is constantly descending, which occasions a continual blast through the port-vent. In chamber-organs there is but one pair of bellows; but they are formed of three boards, in the manner of a smith's bellows, and so have a continual blast. All the internal structure of the organ is concealed from the sight by the front of the instrument, which stands upon the part between the numbers 3 and 6 (fig. 1.)
In every organ the number of partitions LL, MM, &c. there are in the sound-board (fig. 1.) that of the valves V V, that of the rollers s s, or of the levers x y or 8 9 and their wires, and that of the keys ABC, &c. must be always equal. Large organs have commonly four or five sets of keys, beside those that belong to the pedals or large pipes, the stops to which are played by the feet. The keys of an organ are usually divided into four octaves; which are, the second sub-octave, first sub-octave, middle octave, and first octave. Each octave is divided into 12 stops or frets, of which seven are black and five white; the former mark the natural notes, and the latter the artificial notes, that is, flats and sharps. The number of keys, therefore, when there are four octaves, must be 48. Some organists add one or more stops to the first and second sub-octaves. The pedals have two or three octaves, at the option of the organist; so that the number of stops is indeterminate. The keys are placed between GG (fig. 1.), but the scheme could not contain them all. There are also as many handles l l, &c. rollers RR, &c. sliders f f, &c. as there are stops upon the organ; and it must be observed, that between the sliders f f, &c. there are as many sliders on the right hand, and the same number of handles and rollers, and other rows of pipes placed between LN, PQ, which could not be expressed in the figure.
The least pipes and partitions are placed toward the middle of the organ, and the greatest on the outside. The stops of an organ have various denominations, according to the sounds they are to produce; some of which are diapason, principal, fifteenth, twelfth, tearce, cornet, trumpet, French horn, vox humana, flute, bassoon, cremona, &c. There is likewise a contrivance to swell the notes of some of the stops.
When this magnificent instrument is played, the handle O of the bellows is first put down, which raises the upper board T, and gives room for the air to enter by the valve r. Then the other handle O is put down; in the mean time the board T, belonging to the first handle, descending, and shutting the valve r, drives the air through the other valve, up the portvent, and into the wind-chest. Then drawing out any handle, as that of the flute-stop p f, which draws out the slider f g, all the pipes in the set LN are ready to play, as soon as the keys C, D, E, &c., are put down; therefore, if the key D be put down, it opens the corresponding valve m v, through which the air enters into the pipe X, and makes it sound. In the same manner any other pipe in the set LN, will sound when its key is put down; but no pipe, in any other set, will sound till the slider be drawn out by its corresponding handle.
Hydraulic Organ denotes a musical machine that plays by water instead of wind. Of these there are several in Italy, in the grottos of vineyards. Ctesibius of Alexandria, who lived in the time of Ptolemy Evergetes, is said to have invented organs that played by compressing the air with water, as is still practised. Archimedes and Vitruvius have left us descriptions of the hydraulic organ.