Organ (Gr. bpyavov, an instrument), a name applied to several musical instruments closely allied in construction and principle, but more distinctly to the church and concert hall organ, a wind instrument having a great number of pipes of different lengths and sizes, from which sounds are produced by the admission (as determined by keys and stops moved by the performer) of compressed air conveyed to them along various channels from a bellows. The organ (rugab) mentioned in Genesis (iv. 21) was probably nearly identical with the syrinx or pipe of Pan among the Greeks, consisting of a number of pipes placed together in ranks, according to their succession of tones, and sounded by the mouth. An instrument similar to the Pandean pipe was used by the inhabitants of various parts of Asia, and by almost all semi-barbarous nations. The number of the tubes or reeds as seen on ancient monuments varies from seven to eleven. At what periods any considerable enlargement or improvement in organ building began is not cer-tainly known. Ctesibius in the latter half of the 3d century B. C. invented a hydraulic organ, the hydraulicon. A pneumatic organ is also mentioned by some ancient writers. The distinction between these organs is in the manner of supplying air to the pipes.

Mersenne describes an organ carved on an ancient monument in the Mattei gardens at Rome, distantly resembling in form, and in the operation of the keys and the bellows, those of the present day. St. Augustine, commenting on the 56th Psalm, alludes to an instrument inflated by bellows. Pope Vitalian is related to have first introduced organs into some of the churches of western Europe, about 670; but the earliest trustworthy account is that of the one sent as a present by the Greek emperor Constantine Copro-nymus to Pepin, king of the Franks, in 755. Organs were common in England before the 10th century, and are said to have exceeded in size and compass those of the continent. The largest was obtained by Elfeg, bishop of Winchester, in 951, for his cathedral. They were still very rude in construction and of limited capacity. The keys were broad and large, and were struck with the fist; the pipes were of brass, and harsh in tone. In the 12th century the compass of these organs did not exceed 12 or 15 tones. About this time semi-tones were introduced at Venice. In some of the rude instruments of the same period a plan of concords was so arranged that each key called forth not only its own tone, but also, by other pipes, its octave and 12th above.

William of Malmesbury mentions an organ in playing which a wind, " forced out by the violence of boiling water, passing through brass pipes," sent forth musical tones; a device which would seem to have partially anticipated the harsh steam organ, or "Calliope," invented in the United States. Pedals, or foot keys, were added to the organ by Bernhard, a German, in 1470; and in the same century the instrument reached substantially its present form. Among famous builders, the earliest were the family of Antegnati of Brescia, in the 15th and 16th centuries, and after these Serassi of Bergamo and Callido of Venice in the 18th century. In England very few instruments escaped the organoclasts in 1641; at the restoration few eminent builders survived, and foreign artists were called in. - The organ is divided interiorly into four parts, the great, the choir, the swell, and the pedal organ. Some instruments have a fifth or solo organ, while in rare instances there is a sixth or echo. The structural portions of an organ are: 1, the apparatus for collecting and distributing the wind; 2, the mechanism controlling the keys and stops; and 3, the pipes.

The force of wind necessary for blowing the organ is ascertained by the anemometer or wind gauge, consisting of a glass tube bent after the manner of that in a barometer, the lower end being fixed into a socket, the other open to the atmosphere. Church organs without the pneumatic lever are usually voiced to a weight of wind of from two and a half to three inches. The pedal stops, when supplied by a separate bellows, are usually voiced to a wind a quarter or half an inch stronger than the above, which accelerates the speech and improves the tone of the large pipes. The tendency, however, is constantly toward voicing instruments to higher pressures for the sake of the added sonority and brilliancy; and this is greatly facilitated by the pneumatic action hereafter described. The wind, having been collected and compressed, is conveyed to the several main divisions or departments of the organ by means of wooden tubes called wind trunks, and is received into the wind chests The upper board of a wind chest is something like a chess board, with a pipe set above each square. Each row of pipes from right to left is controlled by a stop, within reach of the performer, and each row from front to back is controlled by a key.

If there are 100 sounding stops, there will be from right to left 100 rows of pipes, with 100 perforated boards which slide under the pipes and admit or shut off the wind at the feet of the pipes. No pipe can speak until the drawing of a stop frees the holes at the bottom of the pipes, and a key being struck allows a supply of wind to rush in under the pipes. Each key controls its own separate air-tight compartment or wind reservoir in the wind chest, and each stop has one pipe over this compartment. In the case of mixture stops a cluster of several pipes takes the place of one pipe of an ordinary stop. Besides the stops and keys for the hands to play, there are in organs of the larger class two octaves and a half of large keys placed under the performer's feet, called pedals. There are also pedals and contrivances for moving numbers of stops by one effort, and another pedal which opens and closes a box in which are the pipes of the swell organ. As this swell box opens, the sound is increased. There are also couplers for the different rows of keys. A coupler is an appliance by which one keyboard can be combined with another, or the same clavier can be united to itself in the octave above or below. The sound from each key as controlled by stops varies not only in quality but in pitch.

If the stop drawn be a simple diapason, the sound which each key can give is the same in pitch as that obtained from a key occupying a similar position on the keyboard of a piano. If the stop be a double diapason, a tone is given an octave lower than that from a key similarly situated on the piano keyboard. If the stop is called a principal, the note is an octave higher; if a fifteenth, two octaves higher; and if a mixture, a chord of several notes is given. Thus, by putting one finger on an organ key and by drawing six stops, several octaves of notes and a chord can be made to sound. In large organs of 100 stops, more than 100 notes are played by simply pressing one key. Every sound in music gives out feebly in remote octaves every other note of the scale. (See Harmony.) When these tones, called harmonics, are strengthened judiciously, the result gives the effect of a strong unison note. When a single key is held and 100 stops are drawn, the ear cannot detect the octaves, twelfths, fifteenths, and even discordant intervals which give the strength, they being absorbed in the foundation tone. - Pipes are made of metal and wood.

The chief varieties of metal pipes, as regards form, are the cylindrical, conical, conical surmounted by a bell, inverted cone, and inverted cone surmounted by a bell; while wood pipes are divided into four-sided, three-sided, cylindrical, pyramidal, and inverted pyramidal pipes. All pipes may be divided into two classes, flue pipes and reed pipes. Flue pipes are such as have an oblong opening, called the mouth, at the junction of the body with the foot of the pipe, bounded above and below by two edges called lips. These pipes are made to sound by the wind first passing through a narrow fissure called a flue or wind way, and they depend chiefly on the length or shortness of their bodies for the gravity or acuteness of the sound they produce. Reed or tongue pipes are, on the contrary, those which are made to sound through the medium of a mouthpiece (not unlike that of a clarinet) furnished with an elastic plate of metal. Reed pipes do not depend on the length of the tube of the pipe but on the size of the mouthpiece and the vibrations of the tongue for the gravity or acuteness of the sound.

The pitch of the sound produced by a reed pipe is determined by the number of beats or regular vibrations made by the tongue in a second of time; and the reeds are therefore made small or large according to the acuteness or gravity of the sound each is required to emit. The higher the pitch, the smaller must be the reed and the quicker the vibrations of its tongue. In a flue pipe the pitch is governed by the length of the body of the pipe, or more strictly speaking by the length of the column of air within it. By doubling the length the sound produced is an octave lower. The following table exhibits the number of vibrations which take place in a flue pipe, and the number of blows made by striking a reed in a second of time, in producing the several C sounds used for organ-stop measurement, while to the right the shortened length of the pipe is given:

NAME OF C.

Vibrations in flue pipe.

Blows of tongue in reed pipe.

Length of open flue pipe.

c c c c............

82

16

32 ft.

c c c............

64

82

16 "

c c............

128

64

8 "

Tenor C............

256

123

4 "

Middle C1...........

512

266

2 "

Treble C2...........

1,024

512

1 "

Organ pipes vary in size from a length of three fourths of an inch to one of 32 ft. - The subject of organ tuning is one of great practical importance as well as of scientific interest. In early times, before the invention of harmony, music for the church was written in simple form and without changes of key. The organ then was tuned upon a system of perfect at-tunement. When harmony was introduced and the semi-tones added, the system of unequal temperament was adopted, by which certain of the keys most in use were put in nearly perfect tunc. This made it possible to play without offence to the ear on six of the major and three of the minor scales. The remaining scales were so discordant as to be practically useless, as by that system of tempering each of the black keys was tuned either as the sharp of the white key at its left or as the flat of the white key at its right, but not to do duty both as a sharp and flat. To remedy the difficulty, organs were constructed in the 16th and 17th centuries having quarter tones, so as to give both the sharps and flats each by itself. Of course the mechanism of such an instrument became complex, and the difficulties of playing upon it were greatly increased.

Johann Sebastian Bach seems to have been the first to advocate the system of temperament by which that inequality existing in every octave known as the wolf is distributed equally among the 12 notes of the octave, so that, while none of them are in perfect tune, none are so much out of tune as to be discordant. He wrote his "Well-tempered Clavier " to enforce his theories. By the adoption of this system of tuning the 24 major and minor scales became at once available, and each tone could be made the keynote of a scale. The scale became what it now is, a series of compromises. This system of equal temperament met with long and strenuous opposition on the part of musicians and organ builders. Among its opponents was Silber-mann, the most celebrated organ builder of his day. It was not adopted in England until quite recently. In 1836 George Hogarth, in an article on the organ, said: "The organ in England is tuned on a system of temperament different from that which prevails on the continent, and the effect of which is that the harmony is intolerably impure in all keys which require more than three sharps or three flats," In the system of equal temperament, the pitch of 0 having been obtained, all the thirds, fourths, and sixths that are tuned upward are made a little sharp, those that are tuned downward rather flat; the fifths being tuned slightly flat upward and slightly sharp downward. - The most important of recent inventions connected with organ construction is the pneumatic power, which has rendered possible effects hitherto deemed unattainable.

Organs could not be built previously beyond a certain size, because the performer had not strength enough in his fingers to open the pallets or valves required to feed so many and such large pipes, a force of 20 lbs. in some organs being required to press down a finger key; nor could the wind pressure necessary to produce the power be obtained. Though claimed to be an invention of German origin, and to havebeen first applied in 1825 by Joseph Booth of Wakefield, England, and by the Scotch organ builder Hamilton, this wonderful power, by which the action of the largest organs is made as light as that of a pianoforte, was not fully known until about 1840, when its mechanism was completed by Mr. Barker, an Englishman residing in Paris.

His invention has been improved in England by several organ builders, especially by Mr. Willis of London, who invented the pneumatics or small bellows which act on the slides. The extreme ease of touch which has resulted from the introduction of the pneumatic lever has not however been without its evil effects. Certain organ builders, for the sake of giving to their instruments power and brilliancy, have increased the wind pressure to even 20 or 30 inches. What they have gained in this way in force they have lost in delicacy. The tone of the instrument becomes bold and vulgar, and unfit for accompanying voices. In 1863 Mr. Barker took out a patent in France for an electro-magnetic contrivance to facilitate the playing of organs, and in 1867 he extended his patent to England. Since then various improvements in it have been patented and several organs built in which the action has been used. It is an exceedingly complicated apparatus, combining both electric and pneumatic action, the connection between the keys and the mechanism which works the pipes being made by insulated copper wires.

When a key is struck an electric current passes by means of these through an electro-magnet, the armature of which is so connected with a disk valve as to open it and admit a current of compressed air to act on the pallets. The wires are generally grouped together into one cable, which may be of any length, so that the keyboard may be at one end of the church and the organ at the other. In St. Michael's church, Cornhill, London, the organ and the keyboard are on opposite sides of the chancel, the connection being effected by means of 336 insulated wires gathered in a cable 1¼ inch in diameter, and carried under the floor. The pneumatic lever was introduced into this country by the English organ builder Thomas Robjohn, but its present perfection in many important details is due to American organ builders. It has also been applied to moving the stops of the organ. Now, by the pressure of a small knob within reach of the performer's fingers while playing, whole combinations of stops can be drawn out or pushed in, and the changes from fortissimo to pianissimo made almost instantly and by a single touch. An old invention known as the tubular action has quite recently been revived and improved upon with excellent effect.

It consists in the substitution of tubes of lead for carrying wind to the pallets in place of the old system of trackers. - The largest organ in the world is in Albert hall, London, and was built by Henry Willis in 1870. It contains 138 stops, four manuals, and nearly 10,000 pipes, all of which are of metal. The wind is supplied by steam power. Thirteen couplers connect or disconnect the various subdivisions of the organ at the will of the performer. The organ at St. George's hall, Liverpool, also built by Mr. AVillis, has 100 stops and four manuals. That of St. Sulpice, Paris, is of the same magnitude and has 5,000 pipes. The largest organ in America is in the music hall, Boston, built by Walcker of Ludwigsburg; it has four manuals, 89 stops, and 4,000 pipes. The other important organs in this country are by American builders, and are as follows: Trinity church, New York, built by Henry Erben; Plymouth church, Brooklyn, by E. and E. G. Hook; St. George's, New York, by George Jardine and son; Tabernacle, Brooklyn, by the same; St. Bartholomew's, New York, by J. II. and C. S. Odell; Temple Emanuel, New York, by Hall and La-bagh; and Holy Trinity, New York, by H. L. Roosevelt. These organs have from 2,500 to 4,000 pipes and from 50 to 60 stops, and therefore in point of size will be found equal to the average large organs of Europe. Some of them contain all the modern European and American improvements.

One of the largest organs in America is in the Roman Catholic cathedral at Montreal, and was built by Mr. S. R. Warren of that city. - For further details respecting organs, see Lehrbuch der Orgelbaiikunst, by Prof. T. G. Topfer (4 vols., Weimar, 1855), and "The Organ, its History and Construction," by Rimbault and Hopkins (London, 1870). - The Alexandre organ, so called, being constructed substantially on the principle of the harmonium, will be considered with the latter under the head of Reed Instruments. In the barrel or hand organ, a bellows within the instrument is worked by turning a winch, while by the same action, by means of an endless screw, a cylinder or drum is turned, on which the tunes are set in brass pins and staples, at such distances as required by the lengths and succession of the notes, as in the pins studding the cylinder of a musical box. The pins raise keys, which press down stickers, and open pallets or valves, admitting air to the pipes required. The Apollonicon, built many years since in London, was a gigantic barrel organ, 24 ft. high and 30 ft. broad; it could be played by three large cylinders, or by six performers on as many sets of keys.

The tone was fine, and the effects grand and novel; but the substitution of mere mechanical action for the skill and taste of the living organist was justly deprecated, and the instrument has not come into vogue. The organolyricon is an extremely complex instrument of French invention, much on the principle of the organ, but combining more distinctly a great variety of instruments and effects, in imitation of a tolerably full band or orchestra.