Organs need cleaning about once a year, or oftener if they are kept and used in dusty places. The bellows are suction or exhaustion bellows, and they draw the air in at the top of the organ through the reeds and discharge it below. The effect of this is that if any dust is floating in the air it is drawn in about the action and reeds, where it settles and clogs the working parts, stopping the vibration of the reeds entirely.
The front board or key strip is usually held in place by a screw at each end, but sometimes by slides entering the holes in the side of the case, which may be disconnected by wooden buttons at each end, which are pulled toward the center. The back of all organs may be entered by removing the board at the back of the case, held in place by screws or buttons. Close all the stops, then take your dust blower, if you have one, or a cloth, and remove all the dirt possible in this way. Lift the muffler boards worked by the right knee-swell, take a brush and clean thoroughly next to the reeds which will be exposed when the muffler boards are raised.
If any dirt is left here it will be drawn into the reeds the instant the organ is played. In bad cases, in fact it is better in every case, to draw every reed, letting them lie in a row on the reed board and going over each one separately, brush the dust from it. This will improve the tone, or, rather, the tune of the instrument. Dirt on the tongue of a reed adds sufficient weight to alter the pitch, and if it is removed, the instrument will generally be in as good tune as when it left the factory. Simply cleaning an organ in this way is often called tuning, by inexperienced persons. If it happens that there are only a few reeds that do not speak, and the owner does not care to pay for a thorough cleaning, you will find the silent reeds by the method given under the head “Examination,” and, drawing them, clean and replace.
Each stop on the organ (if there be no dummies) affects either the tone quality or the power of the instrument. The Vox Humana stop affects the quality of the tone by operating a fan in the rear of the instrument or a contrivance contained in a small box, which produces a tremolo effect. All other stops may be said to affect the power. Stops having such names as Diapason, Melodia, Dulcet, Celeste, Cremona, Echo, Principal, Bourdon, Sub Bass, Piccolo, Flute, Dulciana, etc., etc., open certain sets of reeds supposed to give forth a tone quality similar to the instrument whose name it bears, or the tone of the pipes of the pipe organ bearing such names. These stops operate on the sets of reeds by raising the mutes which, when closed, stop the passage of air through the reeds.
The octave coupler stop, sometimes called Harmonique, controls an arrangement whereby, when a key is depressed, its octave is made to sound also. “Forte” stops lift the mufflers or swells, and as these are controlled by the right knee-swell, the Forte stop may be considered of little value. The left knee-swell, called the Full Organ swell, as its name implies, opens up the full power of all sets of reeds and throws on the couplers.