David Reineke, age 12, of Rockford, I11., for his question:
HOW DOES A PIPE ORGAN WORK?
A pipe organ is a keyboard musical instrument that creates sounds by forcing air through metal or wooden tubes called pipes. A pipe organ is the largest and most powerful of all musical instruments.
Many pipes on a pipe organ are so large they must be built as part of the building where they are to be used. A large pipe organ can produce effects of grandeur that even a symphony orchestra sometimes cannot duplicate. It can also play delicate and refined music.
A small pipe organ will have a few hundred pipes while a large one will have more than 5,000. Most pipes are made of lead or of lead mixed with tin.
Most organs have two types of pipes: flue pipes and reed pipes. A flue pipe works like a simple whistle while a reed pipe contains a thin brass reed that vibrates as air passes.
About 80 percent of the pipes in an organ are shaped like cylinders. But no two pipes of an organ look or sound exactly alike. The shape and size determines the sound it makes.
A pipe organ's longest pipe, which produces the lowest note, may_ be more than 30 feet long and one foot in diameter. The smallest pipes are only seven inches long and less than a quarter of an inch in diameter. Most pipes measure less than four feet long.
Most pipe organs have one, two or three keyboards. A few have as many as six. Additional keyboards allow the organist to create a wider variety of musical effects.
The keyboards played with the hands are called manuals. Large organs have up to five manuals. Most organs also have a pedalboard, a keyboard that is played with the feet.
An electric motor provides power for most modern pipe organs. It operates a fan that forces wind into an air reservoir. The wind then moves through a wind trunk into a wind chest. When a key is pressed, a pallet opens and wind enters the key channel. From there a slider, controlled by a stop knob, allows wind to flow into the pipes to produce a note.
A cabinet called a case encloses all the pipes in a wind chest. The case blends the sounds of the various pipes. It provides this combination of sound out of the organ much as a megaphone projects the human voice.
Electric organs have no pipes. Devices called oscillators generate an electric current that produces the tones. The organ's sound is amplified electronically.
An electronic organ cannot create the variety and richness of sound that a pipe organ can. But an electronic organ costs less and requires less space.
The electronic organ has become popular as a home instrument. It is also widely used in jazz and rock music.
Ctesibius of Alexandria, a Greek engineer, built an organ called a hydraulis in 200 B.C. The organ used water power to force air into the pipes.
Organs that used a bellows first appeared in Byzantium, which is now Turkey, during the A.D. 100s.
The major features of the modern organ developed from the 200s to the 1500s A.D.