organ

Oldest of the keyboard instruments, in which sound is produced when a depressed key opens a valve, allowing compressed air to pass through a single pipe or a series of pipes. The number of pipes may vary according to the size of the instrument. Apart from its continued use in serious compositions and for church music, the organ has been adapted for light entertainment.

Only one note is sounded by each pipe. The pipes are lined up in ranks or rows, and are brought into play (‘speak’) by a stop operated from the console by the player. An organ is made up of different manuals (keyboards) that control separate divisions of the organ, each with its own pipes and stops. These separate manuals are the great, swell, choir, solo, echo, and pedal organs, and are controlled by the player's hands and feet. By various groupings and subdivisions of the above, the organ is capable of a wide variety of timbre and volume.

History The organ developed from the panpipes and hydraulis (water organ), and is mentioned in writings that date from the 3rd century BC. The first development of the organ was the supply of compressed air from bellows. Organs were imported to France from Byzantium in the 8th and 9th centuries, and then manufactured in Europe. The replacing of the old drawslides by the key system dates from the 11th–13th centuries and the first chromatic keyboard dates from 1361. Later a keyboard of pedals, played by the feet, was added to control the largest bass pipes. The number of pipes, ranging from 9.8 m/32 ft down to a fraction of an inch, was enormously increased, and they were made in a growing variety of shapes from different materials, and with different speaking mechanisms, each range being controlled by stops that could bring it into action or shut it off at the player's will. The number of manuals (hand keyboards) increased to three or more, which meant that a greater number of stops drawn before the performance could be controlled and varied.

From the late 19th century the bellows, formerly worked by hand, were operated mechanically and devices were invented that could bring into action whole ranges of stops in various combinations. Expression was added by swell pedals producing crescendo (increasing loudness) and diminuendo (decreasing loudness). These are the only means that the player has to vary the timbre either in strength or in quality, the keyboard not responding to changes of touch like a piano.

The electric tone-wheel organ was invented in 1934 by US engineer Laurens Hammond (1895–1973). Other types of electric organ were developed in the 1960s. Electrically controlled organs substitute electrical impulses and relays for some of the air-pressure controls. These, such as the Hammond and Wurlitzer organs, built during the 1930s for the large cinemas of the period, include many special sound effects as well as colour displays. In electronic organs the notes are produced by electronic oscillators and are amplified at will.

organ

The adult human body has approximately 650 muscles, 100,000 km/60,000 mi of blood vessels and 13,000 nerve cells.

In biology, a part of a living body that has a distinctive function or set of functions. Examples include the oesophagus, liver, or brain in animals, or a leaf in plants. An organ is composed of a group of coordinated tissues. A group of organs working together to perform a function is called an organ system, for example, the digestive system comprises a number of organs including the oesophagus, stomach, the small intestine, the pancreas, and the liver. The tissues of a leaf include the epidermis, palisade mesophyll, and spongy mesophyll. The tissues of the oesophagus include muscle, and epithelium.