HARMO'NIUM, a musical instrument of modern invention, for which there arc many claimants. The principle by which the sounds of the harmonium are produced, is called the free vibrating reed, supposed to have been a modern discovery, but now ascer tained to have been known in China long before it was ever heard of in Europe. Its const?uction is as follows: A narrow rectangular slit being made in a piece of brass plate of a quarter of an inch in thickness, a thin elastic spring of the same metal, and of nearly the exact breadth of the slit, is fixed at one end by two small rivets to the sur face of the plate, close to one end of the slit., being so adjusted as to fill the area of the slit, and that when pressed into it at the free end it may pass inwards without touching the end or the sides of the slit, and when left to itself it shall return back to its position of covering the slit, The spring at the free end is permanently bent a very little out wards. A'hen a current of air is forced through the slit, the spring is put into tion, and produces a continuous musical sound, acute or grave, according to the rapidity or slown:ss'of the vibrations. This kind of reed is termed "free," in contra distinction to time reed of the organ-pipe, the spring or tongue of which entirely covers an oblong slit, in the side of a brass tube closed at one end, and vibrates against the cheeks or outside of the slit, instead of within it. After many attempts, in various countries, to construct a keyed instrument of really a useful kind with the free reed, Debain of Paris.produced his invention of the harmonium, which became more or less the model of all the others that have followed. The harmonium occupies comparatiVely but little space, being only about 3 ft. 3 in. high, and 3 ft. 9 in. broad; the depth being , according to the number of the stops. It has a compass of five octaves of keys from C C the key board being placed on the top, immediately below the lid. Under the key-board is the wind-box, on which are valves for each key; while below the valves, and inside of the wind-box, the different rows of reeds are placed. The sizes of the reeds differ, according to pitch, from about 3f in long to +in.; and the quality of sound is affected and modified by the breadth of time vibrating part of the reed, and the shape of the aper ture in the wind-box covered by the valve. The pressure of wind is from a bellows with two feeders, which the player moves alternately with his feet, filling a magazine, similar to the bellows of a small organ. When a key is pressed down, the valve below it opens, and the wind, which bas access from the bellows to the wind-box, rushes through the slit of the reed, and produces a sound which continues while the valve is kept open. is a peculiarity of the free reed that an increase or diminution of the
pressure of wind does not alter time pitch of the sound, but merely increases or dimin ishes its volume. is taken of thispeeidiarity to effect, in ,tie harmonium, u. beautifully expreSsive swell, or diniinntion in the sound, by gradually increasing or diminishing the pressure of the wind. The vibrations of the spring being like those of a pendulum, isochromms, remain fixed in rapidity or slowness, according to the length and elasticity of the vibrating slip of metal, and thus regulate the pitch of the sound without reference to the pressure of wind. For the deep bass-notes the springs are heavily loaded at the loose end, to make them vibrate slowly; while in the higher notes they are made thinner at that end. flart»oniums are made of various sizes, and from one row of reeds (or vlurators, as they are now called) to four or-more rows; each row is divided near the mif:tfie, between au E and F; and each half has its separate draw stop. Lately, a "knee" movement, erroneously called a pedal, for producing a small degree of crescendo on either bass or treble, has been attached. Sonic harmoniums are made with two rows of keys, thus affording a greater variety in solo with an accompaniment; and for more skillful performers, pedal-keys for the feet, like those of a church organ, are added. The manufacture of the harmonium in Paris has, of late years, increased almost incredibly. The various parts of the harmonium can now he got made there, and furnished from a single reed to a complete set. Many attempts were formerly made in England to accomplish time making of a similar instrument called the seraphine„but it was a much inferior instrument, although more expensive. Even now, the harmoniums said to be made in this country, are all got piecemeal from Paris, and put together in London. The best makers in Parii are Debain and Alexandre; and in Germany, Schiedmayer of Stuttgart, and Kaufmann of Dresden. The latter is the inventor of the percussion action for the which consists of a small hammer like that of a pianoforte, which strikes a blow on the vibrator the moment the key is pressed down, and sets it instantly into vibration, thus assisting the action of the wind. Harmoniums may now be had of various sizes and Qualities, at prices .4.:5 to 1:50. Valuable chiefly for accompanying psalmody, they suitably take the place of organs in temporary places of public worship, or among the less opulent class of congregations. For doMestic use, they are not likely to supersede the pianoforte, but possessing the important advantage of not going out of tune through humidity of atmosphere, they will be found available where pianos cannot properly be kept.