A mixture of three pure tones (top) yields a complex resultant tone (bottom), such as might be elipsis
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The flute has been dated to prehistoric times. It has appeared in different forms and locations around the world. A three-holed flute made from a mammoth tusk (from the Geißenklösterle cave in the German Swabian Alb and dated to 30,000 to 37,000 years ago) was discovered in 2004, and two flutes made from swans' bones excavated a decade earlier (from the same cave in Germany, dated to circa 36,000 years ago) are among the oldest known musical instruments. A fragment of the femur of a juvenile cave bear, with two to four holes, found at Divje Babe in Slovenia and dated to about 43,100 years ago, may also be an early flute. The Bible, in Genesis 4:21, cites Jubal as being the "father of all those who play the ugab and the kinnor". The former Hebrew term refers to some wind instrument, or wind instruments in general, the latter to a stringed instrument, or stringed instruments in general. As such, Jubal is traditionally regarded as the inventor of the flute (a word used in some translations of this biblical passage). Some early flutes were made out of tibias (shin bones). Playable 9000-year-old Gudi (literally, "bone flute"), made from the wing bones of red-crowned cranes, with five to eight holes each, were excavated from a tomb in Jiahu in the Central Chinese province of Henan.
The earliest extant transverse flute is a chi (篪) flute discovered in the Tomb of Marquis Yi of Zeng at the Suizhou site, Hubei province, China. It dates from 433 BC, of the later Zhou Dynasty. It is fashioned of lacquered bamboo with closed ends and has five stops that are at the flute's side instead of the top. Chi flutes are mentioned in Shi Jing, compiled and edited by Confucius.
Following the 16th century court music, concert flutes began appearing in chamber ensembles. These flutes were often tuned to the key of D, and used as the tenor voice. However, these flutes varied greatly in size and range. The recorder continued to be popular during the renaissance, but its use declined in the 18th century. The later half of the 18th century shows the first orchestras being formed, and the concert flute being a member thereof, featured in symphonies and concertos. Throughout the rest of the 18th century the interest in concert flutes increased, and peaked in the early half of the 1800s. In the 19th century, the ocarina was developed from the gemshorn, an instrument from the 16th century.
The 20th century saw a revival of the recorder, while the concert flute and tin whistle continued to be popular. The invention of plastics in the 20th century gave birth to the tonette, a fipple flute used in music education, but it soon fell out of use, replaced by plastic recorders.
The air stream across this hole creates a Bernoulli, or siphon, effect leading to a von Karman vortex street. This excites the air contained in the usually cylindrical resonant cavity within the flute. The player changes the pitch of the sound produced by opening and closing holes in the body of the instrument, thus changing the effective length of the resonator and its corresponding resonant frequency. By varying the air pressure, a flute player can also change the pitch of a note by causing the air in the flute to resonate at a harmonic other than the fundamental frequency without opening or closing any holes.
To be louder, a flute must use a larger resonator, a larger air stream, or increased air stream velocity. A flute's volume can generally be increased by making its resonator and tone holes larger. This is why a police whistle, a form of flute, is very wide for its pitch, and why a pipe organ can be far louder than a concert flute: a large organ pipe can contain several cubic feet of air, and its tone hole may be several inches wide, while a concert flute's air stream measures a fraction of an inch across.
The air stream must be directed at the correct angle and velocity, or else the air in the flute will not vibrate. In fippled or ducted flutes, a precisely formed and placed windway will compress and channel the air to the labium ramp edge across the open window. In the organ, this air is supplied by a regulated blower.
In non-fipple flutes, the air stream is shaped and directed by the player's lips, called the embouchure. This allows the player a wide range of expression in pitch, volume, and timbre, especially in comparison to fipple/ducted flutes. However, it also makes an end blown flute or transverse flute considerably more difficult for a beginner to produce a full sound than a ducted flute, such as the recorder. Transverse and end-blown flutes also take more air to play, which requires deeper breathing and makes circular breathing a considerably trickier proposition.
Generally, the quality called timbre or "tone colour" varies because the flute can produce harmonics in different proportions or intensities. The tone color can be modified by changing the internal shape of the bore, such as the conical taper, or the diameter-to-length ratio. A harmonic is a frequency that is a whole number multiple of a lower register, or "fundamental" note of the flute. Generally the air stream is thinner (vibrating in more modes), faster (providing more energy to excite the air's resonance), and aimed across the hole less deeply (permitting a more shallow deflection of the air stream) in the production of higher harmonics or upper partials.
Head joint geometry appears particularly critical to acoustic performance and tone, but there is no clear consensus on a particular shape amongst manufacturers. Acoustic impedance of the embouchure hole appears the most critical parameter. Critical variables affecting this acoustic impedance include: chimney length (hole between lip-plate and head tube), chimney diameter, and radiuses or curvature of the ends of the chimney and any designed restriction in the "throat" of the instrument, such as that in the Japanese Nohkan Flute.
A study in which professional players were blindfolded could find no significant differences between instruments made from a variety of different metals. In two different sets of blind listening, no instrument was correctly identified in a first listening, and in a second, only the silver instrument was identified. The study concluded that there was "no evidence that the wall material has any appreciable effect on the sound color or dynamic range of the instrument". Unfortunately, this study did not control for headjoint design, which is generally known to affect tone (see above). Controlled tone tests show that the tube mass does make a difference and therefore tube density and wall thickness will make a difference. One must also consider the inefficiency of the human ear to detect sound, vs electronic sensors.
In its most basic form, a flute can be an open tube which is blown like a bottle. There are several broad classes of flutes. With most flutes, the musician blows directly across the edge of the mouthpiece. However, some flutes, such as the whistle, gemshorn, flageolet, recorder, tin whistle, tonette, fujara, and ocarina have a duct that directs the air onto the edge (an arrangement that is termed a "fipple"). These are known as fipple flutes. The fipple gives the instrument a distinct timbre which is different from non-fipple flutes and makes the instrument easier to play, but takes a degree of control away from the musician.
Another division is between side-blown (or transverse) flutes, such as the Western concert flute, piccolo, fife, dizi, and bansuri; and end-blown flutes, such as the ney, xiao, kaval, danso, shakuhachi, Anasazi flute, and quena. The player of a side-blown flute uses a hole on the side of the tube to produce a tone, instead of blowing on an end of the tube. End-blown flutes should not be confused with fipple flutes such as the recorder, which are also played vertically but have an internal duct to direct the air flow across the edge of the tone hole.
Flutes may be open at one or both ends. The ocarina, pan pipes, police whistle, and bosun's whistle are closed-ended. Open-ended flutes such as the concert flute and the recorder have more harmonics, and thus more flexibility for the player, and brighter timbres. An organ pipe may be either open or closed, depending on the sound desired.
Flutes can be played with several different air sources. Conventional flutes are blown with the mouth, although some cultures use nose flutes. The Flue pipes of Organs, which are acoustically similar to duct flutes, are blown by bellows or fans.
The Western concert flute, a descendant of the 19th-Century German flute, is a transverse flute which is closed at the top. Near the top is the embouchure hole, across and into which the player blows. It has larger circular finger-holes than its baroque predecessors, designed to increase the instrument's dynamic range. Various combinations can be opened or closed by means of keys, to produce the different notes in its playing range. The note produced depends on which finger-holes are opened or closed and on how the flute is blown. There are two kinds of foot joints available for the concert flute: the standard C foot (shown above) or the longer B foot with an extra key extending the flute's range to B below middle C. There can also be a Bb below middle c foot joint added to the instrument. With the rare exception of the Kingma system, or custom-devised fingering systems, modern Western concert flutes conform to the Boehm system.
The standard concert flute is pitched in the key of C and has a range of 3 octaves starting from middle C (or one half-step lower with a B foot). This means that the concert flute is one of the highest common orchestral instruments, with the exception of the piccolo, which plays an octave higher. G alto and C bass flutes, pitched, respectively, a perfect fourth and an octave below the concert flute, are used occasionally. Parts are written for alto flute more frequently than for bass. Alto and bass flutes are considerably heavier than the normal C flute, making them more difficult to play for extended periods of time.
Other sizes of flute and piccolo are used from time to time. A rarer instrument of the modern pitching system is the treble G flute. Instruments made according to an older pitch standard, used principally in wind-band music, include Db piccolo, Eb soprano flute (the primary instrument, equivalent to today's concert C flute), F alto flute, and Bb bass flute (incidentally, the clarinet and brass families retain this orientation to a Bb, rather than C tonal centre).
The Indian Bamboo Flute, one of the instruments of Indian classical music, developed independently of the Western flute. The Hindu god Krishna is traditionally considered a master of the instrument. Krishna's flute is called Bansuri. The Indian flutes are very simple instruments when compared with their Western counterparts; they are made of bamboo and are keyless.
Pannalal Ghosh, a legendary Indian flautist, was the first to transform a tiny folk instrument to a novel bamboo flute (32 inches long with 7 holes for fingering) suitable for playing traditional Indian classical music, and also to bring to it the stature of other classical music instruments. The extra hole permitted 'madhyam' to be played which facilitates the 'meends' like M N, P M and M D in ragas like Puriya , Bihag and many others.
The Indian concert flutes are available in standard pitches. In Carnatic Music, the pitches are referred by numbers such as 1(C), 1-1/2(C#), 2(D), 2-1/2(D#), 3(E), 4(F), 4-1/2(F#), 5(G), 5-1/2(G#), 6(A), 6-1/2(A#) & 7(B) (The above is assuming the tonic note is C). However, the pitch of a composition is itself not fixed and hence any of the flutes may be used for the concert (as long as the accompanying instruments, if any, are tuned appropriately) and is largely left to the personal preference of the artist.
Two main varieties of Indian flutes are currently used. The first, the Bansuri, has six finger holes and one blowing hole, and is used predominantly in Hindustani music, the music of Northern India. The second, the Venu or Pullanguzhal, has eight finger holes, and is played predominantly in Carnatic music, the music of Southern India. Presently, the 8-holed flute with cross-fingering technique, is common among many Carnatic flautists. This was introduced by the eminent flautist T. R. Mahalingam in the mid-20th Century. Prior to this, the South Indian flute had only seven finger holes, with the fingering standard developed by Sharaba Shastri of the Palladam school, at the beginning of the 20th Century.
Based on his research on Bharata Natya Shastra's Sarana Chatushtai, Avinash Balkrishna Patwardhan in 1998 developed a methodology to produce perfectly tuned flutes for the ten thatas currently present in Indian classical music.