CHAP, v.] THE ORGAN. 185 



II. MECHANISM or THE ORGAN BELLOWS, KESERVOIRS, AND WIND- 

 CHEST SOUND-BOARD AND TABLE CLAVIERS, KEY-MOVEMENT, 



DRAW-STOPS, PEDALS COMBINATION-PEDALS, COUPLERS, SWELL 

 Box, &c. 



The instrumental or purely musical part of the organ being under- 

 stood, it remains for us to point out the arrangement of the sonorous 

 pipes ; how and by what mechanism the performer makes them speak, 

 either successively or simultaneously, in order to bring out the 

 melodious and harmonic effects of the piece which he plays; and 

 lastly how he. uses any particular stop. 



For more order and clearness, we will first describe the general 

 construction and arrangement of an organ : 



The pipes of the different stops are arranged vertically in rows, 

 side by side on rack-boards and inclosed with the necessary mechani- 

 cal adjustments, in a wooden case more or less ornamented and 

 of different dimensions according to the size and number of the 

 pipes and registers. 



Frequently when the organ is mounted on a screen or gallery the 

 organ case is divided and has in front a small case called the chair or 

 choir-organ, containing the registers mostly in use to accompany the 

 voices. The great organ is at the back, the choir organ is in front, 

 and between these two are situated the claviers or key-boards which 

 place the instrument at the command of the organist. 



Wind is given to the pipes by bellows blown by men, or any other 

 motive power, such as water or steam. The air, more or lets' com- 

 pressed, passes from the bellows through various channels or wind- 

 trunks into the reservoirs and wind-chests, and from these into the 

 grooves, boards, and pipes by the action of the pallets. 



The wind-chest is a box, above which are arranged the pipes of the 

 different stops. By pulling out the several draw-handles, placed 

 conveniently for the hand of the organist, called stops or registers, the 

 wind communicating with the pipes of the stop required is obtained, 

 and on the performer pressing down the notes of the claviers, a 

 mechanical movement, called the key-movement, acted upon by the 

 pressure of the keys, opens the valves arranged underneath the 



