(Public domain image from Websters Dictionary 1911)
It is an open tube with circular holes, which produce different sounds when some are opened or closed with the fingers of the instrumentalist.
Types
Flutes fall broadly into four classes, depending on how the sound is produced, and whether the tube is open or closed.
The familiar concert flute, piccolo and fife are examples of transverse flutes, in which air is blown from the mouth across a small hole at the top of the instrument. In a transverse flute the embouchure (position of the lips and tongue) is the main determining factor in tone production (as well as having an effect on pitch).
End blown flutes, include the recorder, ocarina and the tin whistle. These typically have an arrangement whereby the stream of air from the mouth is directed against a blade; embouchure is less critical, though is still important in mastery of the finer points of playing. [Nose flutes]? exist in some cultures.
Most types of flutes are closed-end, rather than open-ended. The organ pipe, ocarina, pan-pipes, concert whistle, jug, police-whistle and bosun's whistle are common examples.
Production of sound
A flute produces sound when a stream of air directed across the top of a hole bounces in and out of the hole. Some engineers have called this a fluidic? multivibrator, because it forms a mechanical analogy to an electronic circuit called a multivibrator.
The stream beats against the air in a resonator, usually a tube. The player changes the pitch of the flute by changing the effective length of the resonator. This is done either by closing holes, or more rarely, with a slide similar to a trombonist's slide.
Because the air-stream is lower mass than most of the resonators used in instruments, it can beat faster, but with less force. As result, flutes tend to be softer, but higher-pitched than other sound generators of the same size.
To be louder, a flute must use a larger resonator, and a wider air-stream. A flute can generally be made louder by making its resonator and tone-hole wider. This is why police whistles, a form of flute, are very wide for their pitch, and while organs can be far louder than concert flutes: an organ pipe's tone-hole is usually eight or more times wider.
The air-stream must be flat, and precisely aimed at the correct angle and velocity, or it will not vibrate. In end-blown flutes, a precisely machined slot extrudes the air. In organs, the air is supplied by a regulated blower.
In a transverse flute, especially the concert flute and piccolo, the player must form and direct the stream with his lips. This makes the transverse flute's pitch and timbre more instantly expressive than any other instrument. However, it also makes the transverse flute immensely more difficult to play than the recorder.
Generally, the quality called "tone color" or "timbre" varies because the flute produces harmonics in different intensities. A harmonic is a frequency that's an even multiple of the lowest, or "fundamental" tone of the flute. When a flute sounds harsh, or whiny, it is being played to provide more harmonics. Generally the air-stream is thinner (to vibrate in more modes), faster (providing more energy to vibrate), and aimed across the hole more shallowly (permitting a more shallow deflection of the airstream to resonate).
Almost all flutes can be played in fundamental, octave, tierce, quatre and cinque modes simply by blowing harder and making the air-stream move faster and more shallowly. Flute players select their instrument's resonant mode with embouchere and breath control, much as brass players do.
The timbre is also affected by the quality of the resonator. Generally, more rigid resonators (such as wood) have a "dead" sound, because they have a higher acoustic impedance, and do not resonate with the harmonics. Concert flutes are expected to produce a "brilliant" sound, with a wide range of harmonics. They are therefore generally constructed of thin tubes made of hard-drawn silver or gold alloys. These are more mechanically elastic than wood, and therefore vibrate in more modes. Theoretically, flutes constructed in thin tubes of elastic but heavy metals, such as alloys of gold, tungsten, platinum or osmium sound "richer" because they vibrate to a lower, therefore more audible range of harmonics. This effect also explains the excellent tone of bronze and brass flutes, which though inexpensive, are less massive, but more elastic.
Appearance and development
The modern concert flute is generally made of silver or another metal, and has a system of keys invented by Theobold Boehm (who gave his name to the system). Boehm's fingering is also used in saxophones, and many flute players therefore "double" on this instrument.
A standard concert flute is pitched in C and has a range of roughly 3 octaves starting from middle C. The other common concert flute is the piccolo, pitched an octave above the concert flute. The alto and the bass flute are availabel, but difficult to play because the embouchere requires more skill. D-flat, B-flat and E instruments are rare, but available.
The precursors of the modern flute were keyless wooden transverse flutes, similar to modern fifes. Later these were modified to include between 1 and 8 keys to aid in producing chromatic notes. The most common pitch for such flutes was/is D, but other pitches sometimes occur. These simple system flutes continue to be used in folk music (particularly Irish traditional music) and in "historically informed" performances of baroque (and earlier) music.
The sound of the flute is characteristic because of its sweetness, and ability to blend with other instruments. These qualities occur because a flute's timbre and pitch are agile, under the instantaneous control of the player.
See also pipe.
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