ORGAN (ante). The pipes are of wood or metal. Metal pipes consist of tin, pure or with some alloy of lead, a common proportion being one-third tin with 'two-thirds lead. Heavy bass pipes are made of zinc. The fused metal is poured into a large box, from which it is drawn through a wide, shallow gate to the surface of a casting table, which may be 2+ ft. wide and 20 ft. long. If the metal have as much as 40 per cent of tin, when cooling the crystalizing tin forms spots upon its surface, and the spots vary in size with the quantity of tin present. The builder varies the quality of his metal to produce pipes of different sonorous qualities as his experience dictates. The material is then cut from the sheet, and formed into pipes on a mandril and very neatly soldered. at the joint where the edges meet. For the sides and backs of wood pipes the builder chooses the clearest seasoned pine; for fronts he uses cherry, maple, apple, or pear. The inside is coated smoothly with glue, to fill the pores and give a more resonant sur face. The stock must be thick enough to withstand the vibrations of the tone without. producing a rolling effect. The speaking length of a pipe is the distance from the lan guage to the end; the pipe is usually straight for convenience of manufacture, but may be• bent in any direction or may even return upon itself, as is observed in the convolutions. of tubes in cornets and horns.
Remembering that musical tones are caused by Vibrations having a fixed and known rapidity, it is evident that a tone may exist in company with other tones whose rates of vibration are 2. 3, 4, 5 times as great, no fractional multipliers being used. The first. tone of the series is called the fundamental tone, the others its harmonics. A trained ear will detect the presence of harmonics in all but the very simplest tones. A which is deficient in harmonics is thin and cutting; a succession of pure octaves has. this quality; the audition of the intermediate tones gives fullness to the sound and binds all together into a more perfect compound. The tones emitted from both open and
stopped diapasons are almost free from harmonics, and the defect is cured by opening at the same time other smaller pipes which yield the hamonics wanting in the larger pipes of stronger tone. The resulting tone has the same pitch as the fundamental, but richer in quality, in which the trained ear may also recognize the harmonics.
The tuning of metal pipes is effected by cutting a slit at the top of the pipe and roll ing the metal down; the tone becoming sharper by this means. The tuner must not be rolled too low, for when rolled back cuts will be left at the sides, which will interfere with the voicing of the pipe. For tuning open wood pipes a sheet of metal is placed horizontally over the open edge covering a part of the orifice; if the end be more covered the tone is flatted, if uncovered the tone is made sharp. Stopped wooden pipes are tuned by a wooden plug, covered with leather, called a tampion: the tampion is depressed to sharpen, and withdrawn to flatten the tone. The scale of an organ pipe is the ratio of its diameter to its tone length. A pipe of large diameter has a fuller tone than one of small scale. Open diapasons have largest scale, and string-toned stops have smallest scale. The length of the foot—the conical part below the mouth—does not affect the quality of the tone. The high cutting of the mouth gives a flute quality to a tone, and requires more wind, but if the mouth be cut too high the tone becomes unsteady; the mouth is said to be eut high when the vertical breadth of the opening is. large. If the length of a pipe be doubled the tone is lowered an octave; hence, reckon ing the semitones, the thirteenth pipe from a given letter has half, or double. the length, as the pipes are counted up or down the scale; but the seventeenth pipe will have half, or double, the diameter, and intermediate pipes diminish in the ratio of the diminution. of their lengths.