HEED INSTRUMENTS 243 out at the time. (See OHGAN.) In the Eng- lish, as in the French instruments, also, the tardy response of the reeds to the action of air is corrected in most instances by a device known as the percussion, by which, the proper stop being drawn, the touching of any key instantly causes the blow of a small hammer on the reed, its vibration, thus promptly be- gun, being then continued by the current of air. In all these forms, moreover, the agi- tation of the reeds is produced by means of more dense or compressed air forced out of a bellows across the reeds, and acting of course against the ordinary atmospheric pressure on the opposite side ; and generally the reeds themselves are placed low in the instrument, often beneath the keyboard, so that the sound is liable to be somewhat smothered or inter- fered with. Some radical improvements were invented by Mr. J. Carhart (see MELODEON), the changes introduced by him having been worked out as early as 1836, and his instru- ments being manufactured in large numbers in Buffalo, N. Y., in the year 1846. In the application for his patent Mr. Peasley had stated that the reeds might be caused to vi- brate by a force or an exhaust bellows, but that he preferred the latter. The instrument did not however come into extensive use until improved by Mr. Carhart. On the principle of the superior fulness and sweetness of those tones in the accordion made when the air is drawn into the bellows, as compared with those formed by forcing the air out, he so constructed the bellows of the melodeon that it should expel the air from the chamber into which the reed passages opened ; this chamber and the space within the bellows freely com- municating, and being maintained while play- ing in the condition of a partial vacuum by means of stout springs, which gradually dis- tend the bellows as often as force has been used to compress and empty it of the entering air. This required that the reeds also should be reversed, the passages admitting air into the exhausted chamber, and the reeds being acted on by the in-flowing streams of air. As a result of this arrangement, all the registers open directly into the one exhausted chamber ; and they are conveniently placed in rows one over the other in the manner of shelves or suc- cessive segments, each horizontal row divided in the middle to form two registers. The con- struction of this part of the instrument finally adopted and now in use is the invention of Mr. E. P. Needham. Again, to open the regis- ters, complicated connections and slides are not required, but simply for each a narrow horizontal door hinged on its lower edge, and directly pulled down by a wire making a sin- gle angle with the draw-knob. The chamber being during performance partially exhausted, if the edges of the several upright shelves or segments and of the horizontal doors to the registers are properly adapted and faced with soft leather, the external atmospheric pressure completes the connection of these parts, and secures air-tightness and strength of the whole ; while in other instruments the condensed air within operates continually to strain and weaken the connections. Thus, in this instru- ment, the parts are readily removed for re- pairs, being stayed by pins only, and as quickly put together again; and the reeds are thus directly accessible. The closing of any regis- ter is made to open a small valve within it, called a pneumatic stop, by which communi- cation with the exhausted chamber is at once made both above and below the reeds, and the latter are then within the exhausted chamber ; but upon opening the register, this valve closes, and thus other communication is cut off above, and the reeds have the exhausted space now only within, the atmosphere acting from with- out. The touching of any key is made to open (if the instrument has but one bank of keys) the corresponding valve in every register. When all the registers are open, all the reeds so uncovered are caused by the entering air to sound ; if some of the registers only are open, only the reeds in these can sound. With two banks of keys, couplers are required in order to put all the registers at pleasure under com- mand of one. When by couplers the keys have thus been connected with valves in all the registers, the drawing of the knob grand jeu, or grand organ, opens all the registers, and affords remarkable power of tone and effect. These arrangements are more common in the larger instruments or harmoniums. The art of voicing reeds by variously curving and twisting them was invented about 1848, by Mr. Emmons Hamlin of Eome, N. Y., and first applied by the Mason and Hamlin organ company of Bos- ton, New York, and Chicago. This invention has greatly contributed to the present perfec- tion of these instruments, increasing the volume and improving the quality of the tones, and producing some of the differences required for the different registers. It is indeed asserted by the German makers that it was previously known in Europe ; but it was not successfully employed there until after the Paris exposi- tion of 1855, where the American reed organs created a lasting sensation. In any reed, the rapidity of vibration, and hence the pitch, de- pend on several particulars, chiefly the length and weight of the reed, and its relative thick- ness at the two ends. If the reed is thick at the free end and thin at the fixed, its tone is deep ; if the reverse, acute. Hence, the reeds are roughly attuned by giving them certain lengths and thicknesses, and then more accu- rately by scraping off a little as may be required from the free or the fixed extremity. The Alex- andre organ is made of different sizes, the largest corresponding to a 16-ft. pipe organ, and by combinations giving seven octaves. Its usual stops are the English horn and flute, and again the bassoon and hautboy, forming the ordinary diapasons, and answering to the com- pass from an 8-ft. pipe; drone and clarinet,
