Keyboard instruments  (Page 3/3)

Aerophones

The oldest keyboard instrument, developed in ancient Greece and Rome and a mainstay of medieval church music, is the organ. Pipe organs get their sound from air vibrating inside a set of pipes. The organ has a source of air under pressure - traditionally from a bellows - and pressing a key sends the air through a particular pipe. The pipe either has a reed held in a frame inside it, or it has a whistle-type sharp-edged hole in its side. The reed or the hole causes a standing wave of vibrating air inside the tube. (See Standing Waves and Wind Instruments for more about this, including an explanation for the differences in pitch between "stopped" and "open" organ pipes.) As with other aerophones , the larger the pipe, the lower its pitch , so just as a piano has a whole set of strings, each tuned to a specific pitch, an organ must have an entire set of pipes, each tuned (by its length) to a specific pitch. Large pipe organs may have many sets of pipes, with each set having a different timbre , so that the organist can vary the sound of the instrument. Large pipe organs are equipped with multiple keyboards (called manuals ); there is usually even a keyboard of pedals (the pedalboard) for the feet. The organist uses stops (switches or knobs) to choose the pipes for each keyboard, and then plays different parts of the music on different keyboards, so that each part has a distinct timbre, as it would if a variety of instruments were playing.

One major difference between chordophone and aerophone keyboards is that the air continues to go through the pipe of an organ as long as the key is pressed, for a constant sound that does not die away, whereas the sound of the strings of a chordophone keyboard dies away (slowly or quickly, depending on the instrument).

Because of its centrality to church music and its ability to play polyphony (multiple independent lines), the pipe organ was perhaps the most important in Western art music through the end of the middle ages and into the Renaissance and Baroque periods. During the eighteenth century, however, composers who were interested in writing complex music began to focus on orchestras and other ensembles instead, and the organ began to fade in importance. Because a full pipe organ is extremely non-portable, most of these instruments are found in churches and concert halls, and its popularity now is also confined to sacred music and classical/art music.

A less well-known aerophone keyboard is the harmonium , which, like a pipe organ, has a keyboard and a source of forced air (often from a foot-operated bellows). Approximately the size of an upright piano or a small organ, and equipped with organ-style stops to change its timbre , the harmonium is often called an organ, but instead of pipes, it simply has a set of reeds. Pressing a key causes the air to flow past the reed that is tuned for that pitch. (The longer the reed, the lower the pitch.)

The accordion also gets its sound by pushing air past reeds, so it is a close relative of the harmonium. Some accordions have a piano-type keyboard, but many do not, and accordions are usually played by musicians specializing in the instrument, not by piano/keyboard players.

Idiophones

There are several important idiophones (non-drum percussion ) that have their played parts arranged in two rows just like a keyboard. These include the xylophone, marimba, vibraphone, glockenspiel, and tubular bells (chimes). These instruments are all played by directly striking the instrument with a stick or mallet held by the player, so they are not not considered keyboard instruments.

The only idiophone that actually uses a keyboard is the celeste , which is a keyboard version of the glockenspiel. A glockenspiel consists of a set of metal bars, each tuned by its size and shape to a note of a chromatic scale . The bars are set in a keyboard-type arrangement, with natural notes in one row, and sharp/flat notes in another. (This is basically a metal version of a xylophone, which uses wood blocks instead of metal bars. In fact, the metal "xylophones" that are a popular children's toy/instrument are technically glockenspiels.)

In a celeste, which usually looks like a very small upright piano,the metal bars are struck by felt-covered hammers when the keyboard is played. The celeste is usually found in the percussion section of the orchestra, where its very bright, bell-like tone is used to provide an interesting and unusual sound, and it is often played by a percussionist rather than a keyboard player.

Electrophones

Recently, electric organs and synthesizers have become favorite instruments in many musical genres and venues. In both electric organs and synthesizers, the sound is created with electrical signals that are turned into sound at the loudspeaker or headphones. An electric (or electronic) organ usually specializes in playing sounds specifically associated with pianos and organs. Synthesizers usually specialize in playing all sorts of sounds, including both imitations of other instruments and sounds which no other instruments produce. A synthesizer may be played using something other than a keyboard (a guitar-like fretboard, for example), but keyboard synthesizers are most common. Both electric organs and synthesizers are very commonly found in jazz and all kinds of popular musics, and electric organs are also common in churches and other venues where a smaller, more portable instrument is useful.